I think we should make sure to distinguish between criticism of concept and criticism of execution. The core concept of Pokémon is as fun now as it was back then, and the feeling of a journey of growth with your chosen Pokémon partners is still awesome. The battle system is solid. Travelling from town to town, seeing a big varied region - also great fun.
However, I think it is fair to criticize the games when, even on a decently powerful home console in the late 2010s, the overworld environments all feel like short and narrow corridors, when there are lengthy and unskippable conversations (that usually add nothing to the plot) along every turn, and where basic options to vary the difficulty are even nerfed from game to game. I think it's fair to call out design decisions such as locking the sound settings behind talking to a random NPC, or insisting that menu sounds from the GameBoy days are still kept around or that the battle camera defaults to a position emulating the perspective of the 2D games. When battles still run on code written for a handheld console in 2002, with all those interruptions of the actions to pop up a text box that tells you what you just saw/are about to see.
The games have not changed much, for better or worse. The concept is still good, but the execution seems more and more subpar. Gameplay has not become smoother or more streamlined - rather the opposite, in the overworld (RBY didn't bog you down with endless talk about malasadas or characters telling you "wow you are a trainer, that's so admirable, I want to be a trainer too but I'm afraid of Pokémon" about twelve times. And when it told you to go to a building two doors down the only street in town, it trusted you to find the way on your own). The core gameplay loop of Pokémon is still fun, very fun, but the user experience has regressed in some areas and barely made improvements in others (obtaining Pokémon for competitive play has been vastly improved, but from an absolutely barrel-bottom starting point, and in remarkably small increments given how long they've been running VGC for). I'm playing it and keep thinking "It's 2020 now. So what's this? ... really?"
It's like ... the game industry keeps evolving, while Pokémon doesn't keep up, and it's starting to become rather noticeable. I mean, there are aspects of RPGs where the Pokémon games still haven't caught up to Ocarina of Time yet (freedom of exploration, size of in-game environments, free camera, to name some), and that game already felt archaic ten years ago. Nowadays games on the Switch can feature open worlds the size of small countries (at 61 km2, the map in Breath of the Wild is as big as San Marino. The Witcher 3 is about twice that at 136 km2, comparable to Liechtenstein). Modern games have cutscenes with stunning visual realism, full voice acting, hugely immersive and dynamic environments, intricate sidequests and subplots, and sometimes (although rarely) even motion capture animation. Well, not all games are like that, but the big ones can at least tick off one or two boxes on that list. Game Freak is still coming to terms with creating towns with building entrances pointing in different directions, and I still don't think Pokémon's character models are affected by light sources. We're still seeing Sandstorm buffeting one Pokémon at a time, separate "taking damage" and "faint" animations with a return to "idle" in between, and "Scyther used Swords Dance!" *Swords Dance animation plays* *boost animation plays while Scyther has returned to idle position* "Scyther's Attack rose sharply!". And at best, somebody will move their arms in a cutscene. Between battles, most of the gameplay boils down to "walk down the hallway to watch the next cutscene, which may or may not involve a battle, and you may or may not have a battle or two on the way there."
Most of us play other games beside Pokémon, and consciously or not, we're noticing that those games tend to look better, sound better, play less clunkily, and generally feel like a more polished game experience than what was the norm at the turn of the millennium. Pokémon still hasn't cleared that bar properly. And it's not like its concept is at fault here, it's the way it is executed. Granted, concept and execution are often closely tied together, and it could be that adjusting one will affect the other, but most of the industry seems able to strike that balance. I think it is fair to expect more from games in 2020, and fair to be a little disappointed when, instead of making any of the required strides in terms of polish, the developers discontinue a few beloved mechanics from the previous iteration and otherwise deliver pretty much the same game over again.
looks at title of this forum thread 
)
I find it fun comparing the estimated numbers on wikipedia for one part of the Pokemon franchise to another entire franchise. Like the card game sales have grossed about the same as the enitre Final Fantasy series. Its not an exact list, but there is some fun to be had looking at this: 
