I think people hate the site because scan groups clean and translate works that they get comissioned to do (paid or freely done out of a hobby) and they're paid a small sum and then sites like mangago come and swoop in and get a bigger buck because they're made a monopoly of the business. ALSO there's hate because the original asian creators (or whoever is the originator) loses revenue...
honestly I can understand the view points, but the internet is a bit of a wild west still and if people are mad simply over money, then you better figure a better business model. I know some artists who get insanely famous because of pirated works... but get mad when americans are looking at their work and had a poor excuse of a method (or none at all) to market to us (or others outside the region).
when they say on commission they basically mean someone probably desperately wanted something translated, bought the raws and paid for the labour. this is mostly because scanlating is actually very difficult and if you're asking them to fit an extra project in, you should expect to pay a price. just like how you'd pay a professional translator to translate something.
on the other hand, most scanlation groups make money via donations. in those cases it's just people who appreciate their work saying thank you. in these cases the scanlation groups have usually bought the raws themselves, and donators often purchase the raws too.
well.. the way I usually see it, the ones who do the commissions usually give the options of which stuff they might translate. essentially saying, pick the one I'll work on the earliest and maybe I'll get to the others.
regardless, this world of scanlations is SUUUUUPER volatile. Not only is there no real business model to supplement people from being upset if sites steal their translations, cleanings, proofreading works..(etc...) but as an outsider, I've seen my fair share of scan groups get upset for working on the same project... or even using their scans for different language translations.
From what I know
MangaGo often steals scanlations and makes a revenue from this site.
Scanlators will upload their work on a specific manga reading website, but it will then be stolen and uploaded here. MangaGo also generates a revenue from ads and stuff.
Which is why the first or last page of a chapter often say to not upload from MangaGo.
Feel free to add or correct me!