Not sure if this is an unpopular opinion, but I believe it's one that isn't voiced very often: The Pokémon games are too successful for their own good.
In negotiations theory, there is a concept called "the winner's curse", and I believe it applies in business as well. Basically, it says you can be too successful. If you're allowed to dictate all terms by yourself, and have no opposition to your policies, you fail to separate good decisions from bad ones. Everybody will nod and smile along no matter what you say (that is, not bootlicking, you've genuinely convinced them your idea is a good one), even if what you say is plainly idiotic. In the end, your own flaws end up becoming the flaws of the system/project/company, and there's no feedback telling you things are heading the wrong way until a disaster happens. I believe the Pokémon franchise, especially the main series games, is showing symptoms of "winner's curse".
As it stands today, the games are hugely successful, and will sell tons of copies by virtue of the word "Pokémon" in the title alone. Their popularity preludes their quality. Their content, gameplay and other qualities hardly matter anymore, almost no matter what they do, Nintendo is bound to earn loads of money every time a main series Pokémon game is released. That's a good thing in many regards, but a bad thing in others, for several reasons:
1. It lets the creators get away with lazy solutions. What's the term, again? "Fat and happy"? Game Freak are allowed to give some parts of the game a slack. We've reached a point where people buy their games because it's Pokémon, not because the games themselves are good. So what if water routes are functionally a mess, if the concept of IVs promotes excessive grinding, if the story is stale and essentially copied from game to game and if the Anime is boring, repetitive and dull. Fans will buy the games despite their flaws. Money keeps pouring in. If sales numbers is any indicator, the system clearly works. No need to make an effort. A good illustration is how Game Freak keeps cutting out features between games, only so they can use their re-introduction as selling points in later games. Game Freak make their games worse on purpose, and still earn lots of money.
2. It stifles innovation. See above. If the current system works well, to the tune of billions of dollars, why change anything? The franchise appears to be a finely tuned money machine, intricately built and set up for optimal enjoyment by players and monetary earnings for the developers. Just look at the sales numbers! The current recipe appears to be the winning recipe, and changing anything brings an inherent risk of failure. The current system brings in the Benjamins, and has done so for several years. The same can't be said with certainty if anything is changed. Thus, the executives are afraid of changing anything. And why should they? Again, the franchise prints money! Well...
3. It masks flaws in the games. Quite self-explanatory. Money keeps pouring in, so how is Game Freak supposed to know when to make changes? There is a whole host of things to complain about with the current state of the franchise, but none of that will impact the sales numbers in any meaningful way. Games will be bought, fun will be had, complaints will be made but ignored. The games all feature the same clichéd story, with only slight nuance differences between games. Certain game mechanics bring nothing but frustration, yet have to be endured or else the player is put at a disadvantage. The Anime is a joke. Stuff like this damages the reputation of Pokémon, but not its profitability. Thus, fixing it is not a very big priority. Especially in light of the next point...
4. It makes it hard to gauge success. Okay, so changes are made. What happens? The games sell like hotcakes. Was the change good? Bad? Did people notice/bother at all? No idea, it can't be heard over the "ka-ching!"s of incoming money. If a game is bad, people might be less inclined to buy the next game, but the response to a change is way too delayed to give any meaningful immediate feedback. Us fans have our forums where we loudly voice our opinions, but the casual players who make up the bulk of the sales might see things differently than we do, and respond differently to changes. What makes a feature good or bad? How well the games sell with/without it? Too bad, the games sell extremely well anyway, so that parameter can't be measured.
Overall, we're left with sub-optimal games, and Game Freak has little incentive to make changes because they earn money no matter what they do. So much more could be done, but they get away with laziness because nothing seems to impact the bottom line. In the worst case, we might end up with a Sonic situation, with gradually worse and more unpopular games, but which still earn their money back and then some because of an excellent brand. That is, until one day the brand is no longer good, the games are no longer profitable, and the developers can't figure out why. "It worked so well until it didn't" is commonly heard in such situations. There will be few indications before the collapse. Efforts to fix the problems often end up being "we must change the recipe back like it was in the glory days", unaware that the "glory days" had the same flaws, only that people weren't as aware of them back then. Still, it's not as easy as just fixing things, because it's nearly impossible to tell if a change is for the better or worse.
All in all, a little bit of sudden rough times - or some competition - wouldn't hurt the franchise, in my opinion. It'd make the developers realize that some effort is required, and that the waterfall of money may one day slow to a trickle if nothing is done. Right now, there are few incentives to innovate and make proper efforts, and the risks appear greater than any potential gains. Why do 5 % more to make the games 50 % better, when the sales numbers appear to remain unaffected? Why not save the 5 %, sit back and enjoy success? Winner's curse, that's why.