I'm not really qualified to give ubers advice, but I want to address your hypothesis.
Yeah, I think the average skill level has skyrocketed in recent years. The depth of high quality RBY players in all tiers is pretty vast (even if the ceiling is similar, I don't want to get into modern greats vs 10yrs ago greats). There's tons of resources available, tournaments are frequent, and the discord is quite active. The combination of these makes idea sharing easy and common, which develops the meta quickly and leads to rapid skill development.
This is visible in the elos. Your screenshot shows your #7 with an elo of 1233. Today, a 1233 elo would be 83rd. So add in meta development, your rust, and a more motivated player base, it makes sense your not having the immediate success you were used to.
I have one replay against you, and there's a few plays and decisions that I would point out as areas of improvement in another forum.
If you want to get better, I have two thoughts:
1) watch high level replays. here's some links to the last three rounds of the ubers tournament in the winter. Note how the players handle their pieces. when do they bring their big hitters in, how do they protect them, how are they closing out games? Also note their team comps - jynx struggles in ubers, although it's not unusable.
https://www.smogon.com/forums/threads/rby-ubers-tournament-ii-round-4.3716579/
https://www.smogon.com/forums/threads/rby-ubers-tournament-ii-round-5.3716968/
https://www.smogon.com/forums/threads/rby-ubers-tournament-ii-finals-won-by-evuelf.3717361/
2) join the discord. link is somewhere around here. There's plenty of people who would love to go through replays with you and point out mistakes and help you improve. Cool crew in that discord, and I don't think I've ever asked for advice and never gotten something useful.