When you consider the budget they have, the copies they are guaranteed to sell and what titles like breath of the wild achieved on the Switch, is there any excuse for it being just OK. Reusing models and animations from the 3DS (I believe) and cutting down the roster of pokemon and then putting out that lacklustre a game. There is no other reason other than greed and disrespect for the fans. Nintendo very much runs with "they will buy it anyway" when it comes to making a lot of their games.
I don't disagree, as a long term player since Gen1 (albeit with some breaks), I don't think the series has developed anywhere near as much as it could or should have done. The underlying charm and love is still there; and you can tell some of the devs really love the games, but the Pokemon Company/Gamefreak really don't give them enough time or enough staff to do the property justice. I blame Pokemon Company/Gamefreak far more than Nintendo though, as ultimately Nintendo are the publisher and shareholder, but they're not the ones in charge of development, and would undoubtedly give them more time per game if they asked for it (given the revenue they generate), but Gamefreak/Pokemon Company themselves seem reluctant to put more dedicated staffers on the development team, and give them the longer development cycle that would really benefit these games.
I have seen reports that part of this issue is that some of the senior management at Gamefreak prefer working with smaller teams as they are easier to manage and control; unfortunately this means that in tandem with the limited development time the games simply don't have the man hours invested they really should given the size of the franchise. As the series sells so well, part of me cannot blame them for thinking they can get away with it.
I really do feel core Pokemon title development moving internally to Nintendo, and a larger development team, would really benefit Pokemon as a whole, especially now expectations have grown. Not only do Nintendo seem to run larger dev teams, but additionally they often take much longer to develop sequels, until they feel it is ready to go, and also own or have close ties with multiple smaller studios who they can draft in to assist with titles when it makes sense (for example the Monolithsoft, Next Level Games and Grezzo guys). Breath of the Wild 2 is a great example; same engine, but they are taking time over it to ensure they do a good job.
A Pokemon title that got the same love and development cycle could be truly excellent, even if they didn't change the underlying core of the series.