I don't see the connection between mobility and grab teching.
Grabs are inherently not very mobile mechanics. They can't be preformed in the air, and only very rarely can be preformed on someone in the air at all or on anyone at any range from you.
Because of this, the more mobile you are the harder you are to grab. If everyone is sufficiently mobile at all times, there would be no need for a grab release, as you would be able to counter getting grabbed by moving better.
Doesn't deal with chain grabs (just don't code grabs that can be chained.). But is something to remember.
In neither of those situations does anyone get grabbed or thrown. Why even have grabs at that point? Like I said, this makes grabs useless, or at the very least it severely nerfs them.
It nerfs them somewhat, but does not severly nerf them.
It is not like you can go 'oh I got grabbed, ima hit z and get out.' You have to hit z before/as you get grabbed in order to escape.
I used to play SF4 casually. And, either way, Smash is not a traditional fighter, nor should it be treated like one. Leave your "Street Fighter does it therefore it's good" logic back with Capcom and SNK.
It has roots in traditional fighter games.
While something coming from a traditional fighter does not mean it is good inherently, (that would be genetic fallacy.) they do give us good things to go off of, and should be treated as such.