The Switch is a hybrid console/handheld, but its games lean more towards console scale games. Part of the selling point of the hybrid model is that you can play console quality games on the go. If the games are just handheld quality that undermines its capabilities as a console.
This is especially the case with adventure games, where they've all trended towards being large scale open area game worlds and longer levels as opposed to some of the games on the 3DS which tended to be more bite sized and linear. And it's not just because of BotW, BotW took another step forward in this direction, but this has been what people have expected of console games for years and years. Pretty much all the way back to the N64 when gaming first went 3D, what kinds of games did they have? Sandbox platformers like Mario 64 and Banjo-Kazooie. Open adventure games like OoT. Console games have been like this for as long as Pokemon's been alive, it goes beyond just the Switch.
Additionally, the games are all being sold for $60 like a console. Remember that on the 3DS, the games were $40, so the 3DS games didn't quite have as high expectations. You were paying a cheaper price for a lower quality game. Now that the games are $20 more, the fanbase expects the games to be $20 better in quality. Indie games like Blossom Tales are not a good example because of this since those all tend to be cheaper than the full $60. As for Link's Awakening, that had the same complaints as LGPE and BDSP, the Zelda fanbase similarly felt the game wasn't enough of a leap from the GB original to justify a full $60 price tag. So overall there's still this expectation that if you're selling a game for $60, it needs to bring the goods. It needs to be a modernized, polished, grand experience that represents the very best of what the console is capable of.
So yeah, even though the Switch is a hybrid, the retail boxed games are all designed, sold, and treated as if they are console games and carry the same expectations of console games. So it's totally reasonable to have expected Pokemon to take a significant leap forward after all previous games were handhelds and they were making games that were largely considered to be console games. They're playing with the big boys now, and everyone wanted the games to act like it.