If MWLL was 'Mech only, I wouldn't be playing it anymore, I'd play MW4 instead.
After all, without the combined arms aspect, it'd be MW4 with shinier graphics but less choice in 'Mechs and, so far, no customization.
So why play an unfinished MW4 when the real one is free?
I won't lie, I like flying, especially dropping some bombs on the head of an LRM/Gauss/LBL/LT camper is really satisfying.
I still pilot 'Mechs most of the time, but without the option to do something different from time to time, MWLL just wouldn't be the same.