Xbox One S Controller help

My Xbox One S is about a year old now, the warranty runs out at the end of this month. I have to admit this is my first Xbox, gave it a try because it was more economical than the other consoles in terms of 4K quality and also for some specific games like
Sea of Thieves and Cuphead. I played both, had fun in them, but that's about all I had. After trying both games I, unfortunately, left it to gather dust as nothing really piqued my interest for the console.

A couple of months ago I wanted to play again, but the controller would not power on at all. The battery had run out a while back, but I kept using it via USB... Yet now, it would not work. I gave up and moved on, tried it now and then with no success. Then
it worked the other day(about 2 weeks ago) while first connected to the laptop and then tried the console again. Even though the controller had new batteries, it only worked via USB cable. I finally got some new 4K movies the other day, but the controller
is back to not working.

I've tried about everything, even cleaned the battery compartment(Had some corrosion from the old batteries) but nothing seems to work. I finally gave in and went into support, but the controller troubleshoot just told me to buy a new controller without
any explanations. I tried to contact the experts(the gamers) and they all just sent me the link to the troubleshooting for the controller. I'm already tired and I just want to know, what could be the problem? Nobody can tell me what is the possible problem
with the controller? Is "get a new controller" all I'm going to get?

Thank you in advance.

EDIT: I tried to do the warranty replacement, but apparently the controller is separate from the console. The console's warranty runs out at the end of this month. The site tells me the controller cannot be replaced and to buy a new one. I also don't live
in mainland USA(PR) and there is no option to send it back.

:)