Thanks for your feedback. You definitely make some good points that I understand, but probably just don't weight as heavily as you do.
1) Gaining critical mass is definitely a barrier to entry for competition. I'm just less sold that Facebook's current popularity is not due to it's foothold in the space vs it's utility.
2) Economy of scale is what allows these companies to offer their services to me as 'free'. I don't really mind that Facebook or Google have taken something that is useless to me (my personal browsing history, locations, likes, etc) and found a way to monetize it if I get to use their platform for free in return.
3) I'm not sure that breaking up big tech would significantly discourage their 'moat maintaining' behavior. If anything, with additional competition introduced, wouldn't there be even more incentive to put time and resource into maintaining what majority they have?