Many of the negative reviews look to be coming from people who seem to forget that pokemon has always been a franchise that is marketed to children.
That being said, as an adult who has played every pokemon game both handheld and on console since pokemon Red, I can say hands down that this is the most fun I have had with a pokemon game since ORAS. From a game play standpoint, things have been simplified and made easier which makes sense for a game aimed at a younger audience. While it felt easy at times, the other mechanics such as raid battles and trying to fill out the pokedex (still over 400 pokemon despite the ones missing) I found myself entertained. Despite this, I still found this game far less linear than games such as X+Y which forced you to go along with the NPCs. In SWSH you have the option to go fool around in the wild area to do raids and power up your team before the next gym challenge.
I by no means find this to be a perfect game. The stamp function seems to barely work. Many players being advertised as seeking something turn up error messages and while in online play there is TERRIBLE lag and staggering (both things I forsee them patching in the future) I still didn't find myself deterred from playing the game.
I would have to give this game an 8/10. It is enjoyable and good fun but some functions could certainly be fixed or improved for a better game play experience.