Welcome to the club. I went through that when they reworked Symmetra, and ended up creating a whole new character, and there was no other hero that scratch the same itch of battlefield manipulation like her.
My solution was taking a 3 month break, but even after I came back as a more casual player, I never again played the same amount or with the same interest in improving. I mostly play for arcade lootboxes and when friends invite me to play with them.
I advice you to enjoy those last weeks as much as you can, take your time to say goodbye to the game you once loved, and then try out the changes. If it don’t appease you, uninstall and take a break. If you miss Overwatch gameplay, you can always reinstall in the future and check it out again.
I’ll probably quit for real after this come live, but that’s my second disappointment. If it’s your first, I think you should still give the game a second chance to win you back.