There are lots of ways to "fix" the DVD player.
Most 5ers and MH use home type surround systems these days that run off AC.
I had thought about replacing my Touch Audio POS with something like
this Pioneer. But last year I used and extra home DVD player because we only watch movies when we have AC anyway as the TV is AC. The aux input works fine for music from smartphones or DVD player. $20 vs. $250. A $50 portable DVD player with 7" screen would work fine too as they have audio/video outputs and you take take it on excursions from the campground.
I hate to spend $250 on a new receiver for the same crappy sound through the stock speakers though. $250 buys a far better sounding 5.1 channel HTIB, again running off AC only. Many of the
portable Bluetooth speakers will sound better and I could take it to the beach.