Yes you can. And you can probably go with 1/4" sheetrock if the walls are reasonably flat. But it's complicated by two things:

1) You need to drive the screws for the sheetrock into the studs, which may be harder to locate because they are behind the plaster and lath. When you are attaching sheetrock directly to studs, you can easily tell if you have missed the stud; this is harder to do when you are going through plaster and lath. Also, you will have to use longer than normal sheetrock screws to make sure the screws go into the studs at least an inch.

2) Since you are bringing the wall surface in by the thickness of the sheetrock, it will change how your molding looks. Normally, you carefully remove all the base moldings so you can reinstall them later and have the floor level detail look the same. However, depending on the style of the window casings and the door frames this may not work. If you don't remove it, then the molding loses some of its profile and may not look great; or you remove it, but then you have complications when you reattach it and the new sheetrock prevents it from sitting properly with the window casings and jambs. How you deal with this is a function of the specific molding details and how much you care about how this looks when you are done.

There are videos on YouTube on this subject, so you might want to check them out to see what's involved.

That's a lot of work and expense to avoid stripping the wallpaper, leaving you with an inferior surface and the problems kudzu outlines when you're done. I'd bite the bullet and strip the wallpaper, then repair the plaster as necessary. Most wallpaper on real plaster comes off pretty easily, just soak it thoroughly with an enzyme wallpaper stripper (use a garden sprayer and give it time), nicking it with a "tiger claw" as necessary. Stripping wallpaper is only really hard when it has been applied to drywall without a primer.

Don’t remuddle the old gal. That will ruin her. You are a steward to the home. Any job should’ve done correctly, without cheesy shortcuts that ruin the home value.

Agree it’s best to remove wallpaper if possible. However. I have an old home with plaster walls, and a bathroom where previous owners put up textured wallpaper and then over the years painted over it several times. We tried everything to get that stuff off, and it simply wouldn’t budge. Eventually we just skim coated it so it was smooth, and painted the room. It’s the main bathroom in the house - even with moisture from the shower the skim coat has held up perfectly for going on two years now.

Sheetrock over the old plaster is a disaster. I will increase the thickness of your walls - the baseboard, cove, around windows and doors. Forget it!

Wagner Steamer - about $50