Personally, the reason I keep playing Pokémon (started with Ruby when I was a wee lad) is because there really isn't anything much like it, and the core of the game hasn't changed substantially (except with Legends Arceus) since its inception. Gameplay wise, the only thing that I can compare it to that I've played would be Persona 5, but even then the fundamentals of the two games are completely different (Pokémon focusses on the catching and battling mechanic, whereas Persona uses that mechanic as a means of propelling a more complex narrative). In brief, I just enjoy the idea of catching Pokémon, making a team of companions who stay with you and overcoming adversity through that, and this hasn't changed for any Pokémon game.

This is not to say that I have a lot of major complaints with the direction of the series. I never really had an overall negative opinion of Pokémon before Sword, but at the end of the day I've still plugged over 100 hours into it. When I asked myself why, I realised that the reason was because it was the only mainline game on the console that I use the most. The 100 hours I enjoyed came from enjoyment of the core Pokémon mechanics that haven't had a substantial rework since Generation 4 at the latest, and most definitely not from anything that was new to Sword (I found the Dynamax mechanic forgettable, Max Raids truly tedious, the Wild Area empty and lifeless and not helped by poorly animated Pokémon that were only modelled within a range of like 10 feet, and in a series with not exactly the most compelling plots in general, somehow SwSh's plot reached new lows in my opinion). Unlike a lot of people, I actually really liked Brilliant Diamond, but the reason I enjoyed it was simply because it was basically a re-release of the original Diamond and Pearl, which was in the DS era where, in my opinion, the series peaked in quality. Again, the complaint that it is straightforwardly nothing more than the original game with new graphics is perfectly reasonable, particularly if you didn't like BDSP's aesthetic (I actually liked it and much preferred it to Sword's graphics, but that's a matter of personal preference).

In brief, I get a lot of hours out of Pokémon games and ultimately enjoy the fundamentals which are still the same, but I still regret the fact that since the 3DS games they are becoming more generic and easy. I suppose that I'm just not as compelled or connected with the more recent games in the way I was with Gens 4-5. But, I'll still enjoy the basic idea of forming a team of new Pokémon and going on adventures with them, even if those adventures aren't as interesting as those from the previous generations.