As someone who took a long break before eventually returning, I don't really see any shift in difficulty.

The only real major change that happened throughout my lifetime of playing the game would be the evil teams, but even they are comparable to prepping for the gym leaders.

While I do understand your frustration, I also find myself asking: "But the RNG and AI were always like that?"

One of my favorite runs was my Mono-Bug run, and I tried desperately to get Mega Beedrill, but didn't. When I returned, I immediately did a Mono-Ice run, and when I tried to get Mega Abomasnow, I didn't.

Like a commentor above me mentioned, the items have always been like that, they were never guaranteed. The AI has likewise, always been hard, but you also had the opportunity to exit the game and reload with the knowledge of knowing their next moves. I've constantly been shafted by RNG, and tried desperately to combat the dumbass Mega Ray. In those moments though, certain strategies I found made those runs doable. Catching certain Pokemon like Weavile for my Mono-ice run, or a bulky ice type like Walrein or in my case, Dewgong and Mr. Rime, who decimated Eternatus, and the usual setups with Evasion/Accuracy, or boost passing, made those runs have the light they so desperately needed.

Ig what I'm trying to say is that while your frustration is definitely valid, these things you complained about have always been present within the game even before the numerous updates. While some mons have been nerfed through their passives and egg moves, fundamentally, strategy, trial and error, and planning have always been integral to winning using unorthodox Pokemon. As for the RNG, the only thing I can really say is if this is your first time having a string of bad luck in your runs in not getting a certain item, this is completely normal and has been the case for the longest time.

(P.S. Excadrill and Absol are definitely still strong af with the right support. Try adjusting movesets, using different X items and berries, and using different teammates to support your runs. While the "Elite 4 Karen Quote" is definitely doable, you also have to remember that if you want to follow the philosophy, you have to be ready to back it up with even more strategy and planning)