The difference is that the problems of the older shows were in other times where the concept of discrimination wasn’t as well defined as now.

The original show tried fighting against violence, racism, sexism, but lacked the objectivity to do so, yes, but it was at a time closer to nazis than it is to us (and let’s not kid ourselves, at a time where americans were much more friendly with fascists than leftists). And TNG was visibly trying to keep a moral aspect to the show, and while often failing they were also often succeeding in surprising ways, to the point of even questioning things like genders, 30 years before the question became a more public one. I have a lot to criticise around it, but the good overweights the bad; this is not the case with recent shows where it’s hard to find a single episode without a dubious concept or production choice.

When Discovery decides to show rape scenes, it is a conscious choice, someone had to say “go on, pretend to be raping him”, it’s not a small mistake. The only similar one in TNG is the early racist episode that even Frakes described as “a racist piece of shit”, but it was what, 40 years earlier? I don’t apply the same judgement on something produced now, where the problems of discrimination, objectification, rape culture, etc, are much more known and defined. It was never good, it was never excusable, but now it is not even acceptable.