Yes, the batteries in the fairbuds are standard LIR1054 which you can buy from loads of places. Not sure about the case but its bigger capacity so it doesn’t need to be replaced as often if ever.
Either way third parties could and probably will make replacement batteries for the case because there is nothing stopping them unlike apple devices. And the battery is still extremely easy to replace.
I agree that a 3,5 mm jack would be nice, but you are overreacting.