(yes I'm reposting)
I cannot stress to you how excited I am to play VGC 2019 in a serious tournament setting again. To kill some time and get in the mood I made a tiermaker of my "current" thoughts on VGC 2019 going into the tour. If there are any significant changes post tour I'll make an update :)
I'll be giving a few blurbs of my placements through S and A+ rank because I think that's where the dropoff point comes in and I think you can tell a lot about someone based on how they rank these 7 Pokemon (maybe the two tiers below but I'm not trying to type that much out now). While of course I am not the single best VGC 19 player, I consider myself very proficient in the metagame and I can probably talk about it more than anyone else because I love it so much.

Easily the best Pokemon in this metagame and it's insulting to call it close. PDon has so many viable sets and moves that it can run, I'd argue way more here than in 2016, and gained so many powerful support tools. My personal favorite sets are fat physical roar and fast modest overheat, but you can run it so many ways and on so many teams. If your team cannot handle Groudon well, it is not viable, because Groudon commands that much respect. Ground and Fire is near perfect offensive coverage for the format, and it has the option to run Dragon Claw or HP Ice if you really want to shoot for flawless. It's nearly impossible to oneshot without a Water move, Z Moves, or a Groudon of your own, meaning it will almost always pull its weight when brought to battles.

I remember when I won my first GS cup competition in 2018 and my twitter followers asked me why I was using Incineroar in a format dominated by Groudon and Kyogre. The answer of course is very simple: utility. Incineroar hardly ever clicks its stabs but the universal value of Fake Out, U-Turn, and Intimidate, further backed by customizable options such as Roar and Snarl, gave every team so much control for so little opportunity cost. It was a great way for Groudon-less teams for hit steels, it was a great Z-Move user on Groudon/Xerneas teams, and it provided many teams a key Ghost resist.

Cover for Geomancy or you lose. Anyone who played 19 knows the feeling of winning seemingly-impossible gamestates with Incineroar + Xerneas + Amoonguss because really that's all you need to enable its potency. When Bronzong and Gengar/Groudon aren't on every top team it's pretty easy for Xerneas users to find a way with their supports and their second restricted, the most deadly ones accepted to be Groudon and Lunala.

Salamence is the best Mega and the best Ground immunity in the format. Even Dragon Claw Groudon variants don't outright check it. It provides teams with a useful Tailwind in a metagame where speed tiers are ridiculously crowded between 90 and 130, an additional Intimidate, and a faster Pokemon than the deadly Mega Rayquaza. Specially Defensive variants that could live Scarf Tapu Lele's Moonblast were very very good at and after worlds. Soft Checked a ton of other minor Pokemon too such as Amoonguss, Kangaskhan, Kartana, and Venusaur.

Unironically if Rayquaza had the slightest amount of synergy with any restricted Pokemon it would be the best Pokemon in the format. Bulky Figy Berry Swords Dance sets pretty much never died unless eating a Fairy move, making it pretty much the most destructive win condition in the metagame behind Xerneas. Also "enables" Kyogre fwiw.

Lunala has three very good sets that make it potent in different ways. Tailwind / Wide Guard / Roar is a supportive god that enables whatever it's paired with extremely well, while still having the nuclear option in its Z-Move that so few Pokemon resist. Psych Up is a sick Xerneas partner for increasing your offensive pressure since the duo is usually more reliant on supports than other cores. Trick Room is another set that works really well on fatter teams like LunaDon.

I might be a bit bold with POgre at 7th but this ranking always felt right to me. Kyogre's really scary if it hits the field at a good time but sometimes it's forced in too soon, takes too much damage, or just otherwise struggles if it can't just click Spout. I'm a bit biased because I played Lunala almost all season which naturally has a good Ogre matchup, but I think if we did a proper survey/ranking it wouldn't be much better.
I will be back post VGCPL for some more VGC 19 analysis/discussion. I encourage those who are playing oldgens to use this thread to share your thoughts and adventures :)