Try a set of .009s, and listen.
Sounds different to .013's.
Every-one has their own ideas on
slide playing.
But heavy strings sound better even when playing standard, imo.
As for heavy strings being a "crutch". well, sounds like your friend is a little bitter, and he may have a bad case of sissy fingers! (lol).
Maybe he uses a lot of distortion?
I can use a light touch and slide with .009's easily if I want to, (and have on many occassions on friends guitars) but I don't like the thin tone.
I'd hate a world where everyone does things the same way though.
Whatever floats your boat.