The problem is that I suspect that BW1's early game mons (especially the ones you mentioned) being underwhelming/boring/bad was intentional, because I'm firmly convinced especially upon recent studying of the game's structure that the early route mons were designed with the philosophy that you will eventually replace them with better mons who show up later in the game.
Patrat and Purrloin, especially the former, are very obviously meant to be Rattata: early bloomer who evolves once at Level 20, and Watchog will be pretty strong for the early-mid game especially since that's around 3 gyms in, especially with early Crunch and later Retaliate/Return not long after to serve as a hard hitter for the early game, but as the game goes on, it and Liepard will begin to fall behind and be replaced by better mons who show up later on such as Scrafty, Cinccino, Bouffalant, etc. Some of the later Normal or Dark mons evolve around the 30s or are obtained around that level, which is when you start to see Watchog and Liepard falling behind.
The others you mentioned are quite similar cases. Munna is known for being part of the stone evo dilemma, but I suspect the intended experience in using Munna in BW1 is you should evolve it soon after Lenora gives you the Moon Stone at the end of Pinwheel, around Level 19 when it gets Psybeam. If you evolve it right there, it's basically a hard carry early game with its godly bulk, Yawn, and Psybeam hitting off of a high Special Attack making it a powerhouse early on. Because you evolve it there, Musharna loses the ability to learn any moves by level up, so now that's the peak of its potential. But when you look at the later Psychic-types, namely Gothitelle, Reuniclus, and Beheeyem, who inherently reach their potential later, and learn much stronger moves later and have better coverage options at their disposal. All of these Pokémon evolve in the low 40s, which is when you'll start to notice the power drop with Musharna's Psybeam. At this point you will likely replace Musharna with a better Psychic-type at your disposal, whether that be Gothitelle or Reuniclus. Woobat is a lesser case but that's a case where the mon is okay mid-game but it falls of hard late game because its stats simply don't cut it anymore, and of course Gothitelle and Reuniclus are way better in the late game.
The monkeys are alike to Musharna in a sense: you get the stone for the monkey you got around 3 gyms in and they get their upgraded STAB around Level 22 which you can feasibly reach during Castelia, and from there you should ideally evolve them right away. Once they evolve at Level 22, they're actually very good. Simipour in particular is a nuke with a hard hitting Scald, and Simisage and Simisear also get by on raw stats and a relatively strong STAB plus all three of them have great coverage to give with Work Up and TMs making them very strong throughout the mid-game. They start to lose a bit of steam after Brycen, which coincides with later mons of their types reaching their potential: up around the high 30s is when they start to fall off, and that's close to when you can get mons like Sawsbuck and Ferrothorn (for Grass), Chandelure or Darmanitan (for Fire), and Jellicent (for Water) fully evolved. It's at this point that you would ideally be inclined to replace the monkeys with the respective better mons of their breed. That is aside from the fact that they're basically there as a tutorial for the first gym. Throh and Sawk are mostly meant to be tutorial mons for Lenora, but granted they're competent for the early game albeit boring.
Sadly most of the early route mons in BW1 are underwhelming because they're meant to be, so that you will eventually move on to better mons as the game progresses. BW1 really tried to emulate Gen 1 in many, many ways because part of its gimmick was it was a "soft reboot" meant to invoke the OG Kanto games' vibe, and Gen 1's Pokémon were all designed with this design philosophy in mind and Gen 5 attempted to emulate it. The intention doesn't come off as well in practice, unfortunately, because most people are inclined to just grab a select group of six and roll, rather than rearrange their team on a consistent basis and discard early catches for later mons.
Gen 5's evo levels were designed with a very particular modus operandi, which was essentially that every mon spends around 10 levels in each evolutionary stage from the moment you got them to the point where they evolve. The idea is that you would develop an attachment to each stage as you put in the effort to raise the mon and it would be more rewarding once they finally do evolve.
Especially with the late game Pokémon. I alluded to it in the past but I really think the designers aligned the late evo levels not to the first time you reach the Elite Four, but the second time, which is when you actually do get to battle Alder. Most of the late mons like Mienfoo won't make it in time for the first Elite Four run and the N's Castle segment, if at all, but they will evolve in the post-game most likely when you spend your time training your team (Granted there's a big spike in levels in the post-game since everything is Level 60+, but fortunately many NPCs used unevolved mons which are perfect training opportunities for your unevolved Rufflet, Vullaby, etc. to get some EXP, and given the EXP system getting the late mons to their evo levels is easier in this game because of the inherently high levels of your opponents), until you eventually reach the high 60s/low 70s for the Elite Four rematches and Alder. They evidently want players to do the entire post-game segment and challenge Alder, and I think the idea is that you would have even more evolutions to look forward to while training your team during the post-game for Alder and your team would continue to evolve and grow as a means to incentivize playing the post-game half of the adventure.
Ideally they would likely rotate out an earlier catch that eventually doesn't cut it anymore. By the time you reach N your team would likely be something like Starter/Chandelure/Haxorus/Krookodile/Reuniclus/etc. and a bunch of other mid-late game catches depending on what you actually used, and once you reach Alder it should be something like Starter/Hydreigon/Volcarona/Braviary/Legendary with other late-evo mons plus some mid-game mons you likely opted, ideally maybe Reshiram or Zekrom too.
Of course, the big problem with this approach is that the high evo levels, while workable in the context of Gen 5 itself, are absolutely horrible for future compatibility. It's especially bad when you have a case like Gen 7 which allowed you to get Rufflet and Vullaby very early in the game at around Level 10, but because of their high evo levels they will spend far more time unevolved than is necessary and don't evolve until close to the end of SM/USUM, essentially forcing players to drag an unevolved mon around for an unbelievably long time.
Looot of rambling but the big takeaway is that I feel that Gen 5's Pokémon distribution and design was very likely intended to be that you keep catching Pokémon along the way on each route until you eventually build a strong team at the end, but outside of your starter your other five slots are always changing at every time but throughout it you should have a strong group of six for every point of the game, but it's never a fixed group. Unfortunately, this isn't how most people play and it's not the most intuitive manner of playing the games, especially when there's an intense psychological threshold you have to overcome to discard/box a mon and replace it with something else. Especially when it's a stark contrast to Gen 4 (Platinum especially) where you get a lot of good mons right off the bat and you can form a fixed group of 6 right away with a bunch of good mons and roll with a good variety all the same.
