Nope, you can go back and play those games now and they're just as good. People who claim otherwise are just writing apologetics for modern gaming industry decline. Or so retarded they actually prefer braindead pablum to proper design.
Dude, you're talking about games with braindead combat apart from a few mage duels. Sarevok, Firkraag, Kangaax, Irenicus end battle, ToB end battle and Demogorgon. Those are probably the only challenging fights in the entire series.
I agree they were enjoyable, but they were far from flawless, or even "proper design".
Also, the Sandthief's Ring in BG2 had a limitation of one use per rest. It wasn't constant invisibility. That's quite a bit less powerful than a cape that can turn you invisible multiple times per battle. The BG1 version was actually more powerful, since it had multiple charges. You just needed to sell and rebuy it before the charges ran out, but that could cost you tens of thousands of gold each time.
The item in BG2 that offered constant invisibility was the Staff of the Magi, and you needed to beat a room full of high level opponents to get it. Probably higher level than anything in BG3.