Sadly this is quite common, as DL cuts corners and defers maintenance on its aircraft on things like interior/seats. You must - MUST - always check your seat and recline it fully and bring it back up the moment you board. And you really need to board as soon as you can. So if the seat is broken there is enough time to dispatch for techs and try to fix it, or switch your seats.

There was a time when I had a broken seat in about half of all DL flights for a while (that was a few years ago, though).

You chose not to test your seat when you got on (something that any seasoned DL, or for that matter any airline, flier knows to always do), so you never gave DL a chance to reseat you or fix your seat. That being said, of course you deserve more than just 10K miles; at the very least you need to get the fare difference between basic economy and full fare J either as a refund or at least as a Delta flight credit.