I kinda like the retro look now
If you wait long enough they will become genuine antiques!
Modern budget kitchens leave me cold.
The question is are the units still sturdy and can they be kept clean. If tenants are happy then just do the minimum to keep it reasonable.
We moved a 70's schrieber kitchen about 20 years ago from one room to another. (This really grated the workman at the time as he thought we should have got new) New worktops and tiles and it looked great. We moved out but the original units are still going strongish. If we had replaced it with new units at the time it would now be twice as knackered as the current ones.