tl;dr Games were sold as a package where the integrity of story played a big role, and there were more types of them. Gachas try to sell every character as a separate product, and it often hurts writing and storytelling. Gachas are also lazier about MCs and more reliant on self-insert.

Is it a paradox?
If serious, I think the actual problem here is a lack of diversification between audiences which used to be more prominent in the date sim/VN scene.
Like, back then you'd have very simple romance date sims, you'd have otome VNs and eroge VNs, you'd have gen VNs with full plot focus. So everyone could stay in their lane.
Gachas kinda lack that diversification and "oh we should appeal to THAT audience at the expense of the character writing we feature in the other parts of the game!" is prominent. Because every character is a separate product and you can never be sure what you'll get.
And for full gen without the "pandering" aspect and without secluding genders there's what... Reverse 1999? And that's it?
If all these games were straightly advertised as date sims, then I'd have zero questions. But they're advertised as fantasy RPG's, not datesims or even eroges.

I'm also not against stuff like Blue Archive -existing-. I just personally keep away from it because I know it's depiction of female characters is something that wouldn't sit well with how I view female characters. It's cool people have them. Though I don't really get how do people enjoy the pandering when it's delivered so unconditionally you know they're just trying to make you feel nice... Isn't it like being lied into your face? Oh well, I digress.

There's just the quality of the MCs, too. Let's take Fate. Shirou's romances are nice to read because he's an actual character. Guda's romances are cringe to read in 80% of instances because the MC doesn't even have a proper personality for you to understand why all these awesome women would be after them. I'd be after Arash if I were them, you know! He's also a great guy who'd listen to my problems! And that's like the only character trait Guda has consistently.
(There's 20% which surprisingly work. Like Corday)

You can take the harder route of "yes, I'm writing why these characters would totally fall for each other", or you can go the easy route "everyone will fall for ~you~ because you're nice :3"
VNs weren't as shameless about having a black hole for an MC. Or at least those that were didn't make it big enough for anyone to care.

I'm also a True Route Truther, and I believe relationships between people are meant to be special and unique, and when I'm told "hey, you can have the same relationship with 100 different characters" I stop believing in all of them.

RPGs are closer to the given example. Silent protagonists for association were a thing since forever. I think it just didn't leave as bad of a taste because it rarely affected all the characters. RPGs were sold as an integral game product, gachas try to sell every character but NPCs as a product and it often affects the integrity of their writing in relation to the story.