it is hurting sales and brand, the underlying problem is that to dramatically increase performance requires recomping both the tech team and the management and likely also the executives whose decisions shape and limit the org in the first place. In any org, the #1 priority for everyone involved is to keep their salary flowing, which means not replacing themselves with someone better.

This sounds like a lead/architect issue. If you can't roll out a custom UI component library, use one of several mature libraries that already handles these cases. Accumulating tens or hundreds of thousands of lines of UI tech debt is not an Agile issue.

Here is the correct answer to this, buried in the comments.

Can you explain this further? What library are you talking about?

Why do you not have any power to fix it?

Essentially all work is driven/prioritised by the product owner and is signed off by a product council. I can't instruct the team to spend time on things not on the backlog.