But there are libraries that a bad dev can make fast software with. You can accidentally make a laggy textbox in one framework more often than another, that's why what framework you use matters. The textbox is just an example, there are myriads of ways the DOM can behave badly without the developer having any intention and possibly the application layer logic is perfect.

Each framework has its quirks. Do you optimize for correctness or speed? Does every update need to be 100% correct/consistent or can you allow it to drop updates? These are performance details that the framework should provide tooling to deal with, or it may not, and it may have abstracted away all these decisions and made it impossible to fix the textbox lag unless you hack into the DOM manually. Which framework you use matters a lot.