I'm like the voice of doom on these threads but Shellac absolutely destroyed my nails and I'm someone who normally has naturally strong, long nails. Great whilst I was using it but the minute I stopped my nails fell apart. I had flaking, splitting nails that took months to recover.
In my experience in absolutely does damage and weaken the nails. My shellac experience means I would never use any kind of gel again. A couple of years on and my nails are back to their normal talons.
Was it a recent experience with Shellac? It's improved a lot, I believe. I spoke to someone who had a similar experience to you, a few years ago, but has had more success recently with it.
I think, though, bottom line is that there is no product which will have exactly the same effect on everyone who tries it. We are all completely unique, so it's not a guarantee of success/failure but an indication of possibility, when we explain our experience.
I'd never use gel again - my one experience of it was enough. I found it too thick and artificial - couldn't feel my natural nails at all. It took two attempts to get it working as with my super-bendy nails it kept lifting.
Whether going for gels, acrylics or Shellac, if you are like me and have nail beds which are quite thin, I think it's essential that the buffing to roughen the surface is only gentle.
As jordie tart says - don't pick! If you use acetone or proprietary remover - make sure you've got your cotton wool well soaked - it should feel wet. And be patient - leave it on for several minutes. Then use an implement which glides across the surface of the nails to dislodge it, and don't dig in. If it doesn't come off in the first go, reapply your remover to soften the rest of the polish/gel. Actually - it's pretty good advice for taking off any glittery nail polish, to be honest.