What's the legacy codebase, if I may ask (unless it identifies the company too much)?
The webforms stuff isn't much better because the code quality is the worst I've ever seen. Adding features and fixing bugs is a stochastic process because you never know what will break.
Usually fixing a bug will expose an old fix that was done improperly for the original even older bug, forcing you to undo multiple levels of hacks to implement your own. It's nightmarish
Legacy codebases suck, but it doesn't stop newer codebases from sucking just as much. I've learnt that the hard way.
It's the culture more than the tech that causes this to happen. Every time I offer to refactor I'm told to fix it the fastest way and that's how we've been doing it for 10+years.
Ok, as someone with a strong dislike for modern js I still feel sorry about this.