You can add back some life with wood,,,
Cut up a 4'x 8' plywood, or cheaper stock, and you can have 4 - 2'x4' panels for a bit of reflection,,
Put em on stands, find where they best suite your recording / playing position
I did my whole garage for 'the band" in egg crates, (egg farms don't smell so great, lol)
ANd some 1 inch fiver board for the entree,,,
It wasn't too dead but the drummer need a bit more since he couldn't just turn up,,
I added some plexiglass panels I had and some plywood around him on stands.
He said it was the best his kit ever sounded while playing..
Had to move the panels so we could still hear him, but we didn't have to reach 120db just to practice anymore, lol,,
I knew none of what I know now, so things make better sense now.