DMs Revenge is spot on.
I got started with 3.5 and moved backwards to 2e, while dabbling in 3.5 to this day, so I definitely know your pain of large statblocks for everything. If you’re doing 5e I would just read over the monsters and make a note of what important abilities the monsters have and translate them as well as you can. It’s worked fine for me (and as far as I know 5e is almost as easy to homebrew as the old stuff), hell I have a small folder of various 3e and Pathfinder monsters I ported into AD&D. It’s easier than you’d think and my players have yet to realize what’s homebrewed and what’s not.