As someone who grew up playing pokemon from Red and Blue to the newer generations I would say Temtem is a no brainer. the Pokemon games got very easy from gen 6 (X and Y) onwards. Temtem offers a much higher difficulty than the pokemon games requiring you to use your brain in battles. Just using your starter will not get you far in this game. There is not one Temtem with a design I have looked and thought "what were they thinking?" and all the Luma (this games version of shinies) look awesome.
The dialogue is quirky and funny. You can end up having a full blown conversation with some random trainer along one of the routes with multiple dialogue options, this game was made with love for sure. saying its a rip-off of pokemon is doing it no justice, sure it's inspired by it but Temtem had a different feel than Pokemon.
If you are looking for something similar to pokemon but with more challenging gameplay, lack of hand holding (from the newer games at least) this game is worth both your time and money.