I don’t know if grading inflation has gotten worse- maybe it has- but it’s always been a problem for used records. Play grading is the only arguably safe way--brick & mortar transactions that give you the opportunity to inspect may be better than online transactions, but a lot of damaged records can look fine and play horribly. (The calibre of TT/cartridge set up in some brick & mortar stores also makes me reluctant to play test the record on such machines. Same at shows).
Craig Moerer (Records by Mail) is an established seller with a large inventory and is consistent; he typically grades everything VG+ on media to be conservative. But he doesn’t have everything. (I did buy a Vertigo Clear Blue Sky from him that is quite rare for $50 dollars- he cataloged it as a reissue, when it was an ex-UK pressing, not a reissue).
I rarely find what I am hunting in stores, though I’ll buy stuff that I’m not "looking for"- same with shows, which may have some of the stuff I’m chasing, but often at nutty prices. (You can negotiate, but if the starting price is 2x market, why bother?)
I buy mostly online- I have a dialog with the seller if it is a high value record- it will tell you much about their knowledge and approach. If it's is an expensive record, they will often play grade at my request; sometimes, they downgrade their rating and offer a price break (I don’t usually go for that bc i’m not looking for a cheaper flawed copy); sometimes, they are candid and say "this isn’t the record for you." I don’t think most legit sellers want to go thru the return process any more than I do.
It isn’t foolproof- LPs are by their nature almost inherently subject to flaws, but a discussion with the seller- confirming deadwax, condition, warps, etc. is a pretty good way to reduce if not eliminate some of the more common problems. (A lot of times, the information about the pressings is wrong in the listings- get the deadwax and label if it isn’t listed /shown to confirm). That said, I still get the occasional clunker. If it is a cheap record, I don’t waste more effort on trying to return, negative feedback (though I will write to the seller privately); if an expensive not cheap record I will return, but it is a pain.