Yeah I'd say it's absolutely fine as an entry point, has the exact same Pokemon formula you would expect.
My niece (10) is playing Shield and while she loves Pokemon she never really gave a shit about playing Sun and Moon, quit at the first town and only really cared about changing her characters hair and clothes. She's been really into this one though, Eevee and Pikachu are still there and she likes seeing ones that are new to her as well as the returning mons.
My Nephew (6) has been using my copy of Sword on a seperate profile to play along with her and he just skips all the story parts but loves catching. It's all he wants to do whenever they come over. I find I can just let him run with it when hes catching, its easy enough for him to figure out what to do and what moves to use.
My niece used to collect Pokemon cards so she knows a lot of the old Pokemon, doesnt seem too bothered by the cut. I mean theres still over 400 and I doubt she will be interested long enough to even catch anywhere near that many. She knows Jigglypuff is gone but she was marking out over a fucking Magikarp being in so its give and take
