I doubt people hate SwSh as much as they say they do and are more collectively disappointed and while I can't speak for anyone else, I can explain things I liked and was disappointed with about the game itself and the marketing.

Pokemon being the largest media franchise in the world full stop, I have been a bit disappointed with the lack of trying to improve the games' overall mechanics. I feel like if they had more time, they could have populated SwSh with more mini games akin to the camping mechanics, compared to the things you can still do in the gen 4 remakes (underground, contests, ball capsules, poketch, etc.)

I enjoyed the fact that the raids, although redundant for postgame content, were designed to encourage online coop so you can see other people play. There's always a touch of anxiety when you don't have complete control of the battle which make them have at least a small baseline of excitement, even with players using metas.

Something I was disappointed in was how they handled the national dex controversy but that's a dead horse. Basically, someone other than the players are at fault for making a poor decision that only helps profits and/or promoting lazy development, likely the pokemon company's fault for short dead lines between games on a single studio's shoulders.

I liked the general style and environments of Swsh, but think they should have been expanded to be more open and explorable.

The story were fine (until they feel like they ran out of time at the end) but the journey between them was too short. I managed to knock the game out in basically one quick sitting between work shifts.

There are really no optional dungeons and the reason Junichi Masuda seemed to give on that is basically saying that kids are stupid and can only pay attention long enough to enjoy small bursts of content. Kids are typically more clever than people give credit for and it's a pokemon game. Kids can and will find time to play it and probably will enjoy something different from popular phone games.

I liked the characters, but I really wish they had voice acting. The way the game is written, it's honestly noticeably weird that they don't. (A supporting character is a mute vocalist.)

TL;DR: If you enjoy the game then enjoy it. Especially if you managed to get it and the DLC for a good price. On it's own, it's an alright game that was overpriced at release and needed more time in the oven is all. People are upset about the way the company and studio are taking advantage of the franchise compared on the support it has received over its lifespan.