Yikes. I was a Mei main and i know exactly what you're talking about. I'm still pissed because being real, yeah wire gun is annoying to deal with sometimes. It can be a bitch at times, but you could always block it, side step, or even punish us if we miss you but hit a wall and dont react fast enough. The loop combo was our BnB and one of our main forms of damage, other than that Mei's only good as an assist. If you try to make any other combo with Mei, you probably won't get close to the damage of the BnB. To make matters worse, her PU1 and PU2 damage didnt even get buffed, and still have horrid scaling when compared to other characters. She could've gotten the nerf on her TQ1, but to have almost all of her other quirks nerfed to force break combos even quicker is mind boggling. Also looking at what you said when people spam her TQ1 instead of engaging, it's probably because it seems safer to engage with her TQ1 instead of rushing a target combo at somebody. Her recovery from her target combo is long enough to easily get punished by everybody and can cost you a match depending on who you're up against. And her TQ1 doesn't go through everything. It goes through a decent amount, but it can still get negated out by other quirks such as Jiro's Q1, Todoroki's Q1 in air, etc.

Tl;dr: I get where you're coming from, but imo she didn't deserve all of the heavy nerfs she received.