Perhaps controversial here, but in general, I've found developers who are having a hard time supporting browsers like IE11 tend to be the ones writing frontend

Perhaps controversial here, but in general, I've found developers who are having a hard time supporting browsers like IE11 tend to be the ones writing frontend code poorly. JQuery is a great example of how you can create a library with some core functionality and know with 100% certainty that if you use it correctly it will work across all browsers that it was intended to support. Whenever we have issues with browser support where I work it's almost always because a dev has gone rogue and decided to build something with a heap of vanilla JS instead of using or extending a library with cross browser support in mind. Perhaps you need to ask why you're having so many issues when so many libraries and frameworks will support IE11 out-of-the box if you use them correctly.