They can shoehorn the ST in all they like, I'll never buy into it. It's just a shame they're trying to do it in The Mandalorian, something I like. It's just going to cause a distraction. Tbh though if we'd only ever had The Force Awakens, and hadn't had the two atrocities that followed, I'd at least have had a bit of interest in seeing Snoke and the rise of the First Order. They could've done something interesting with it. However, now that we know Snoke was a meaningless character (not Plagueis like he should have been!) what's the point of a backstory? I really don't see the point in forcing them into the story 20+ years before the ST even takes place. It all just feels so unnatural and inorganic at this point.
At the end of the day it's best to consider everything Disney as its own separate thing, it's not ''canon'' imo. If it didn't happen under Lucas, with his involvement, supervision, permission, or input then it's all ''fan'' fiction, or someone else's interpretation. For that reason they could never ruin the legacy characters for me, we already have what we have before Disney came along. The EU has far more of a claim to being canon imo, Lucas, whether he liked certain things or not, signed off on all of that. It really pisses me off when you have Kathleen Kennedy and her dreaded story group coming in and wielding the axe, with the approval of her buttkissing little fanboys/girls, telling us everything we've grown up with for 30+ years doesn't really matter. I hate the dismissal of the EU from the Disney era fans. Sorry, totally veered off the point there, rant over!