I suspect the simplicity and exaggerated forms are because corporations want their logos to be clearly visible when viewed on a tablet or mobile phone screen.
I don't have any artistic opinions on this content; it's not meant to be 'art' afterall. It surprises me that there are people who are upset about it; of all the evils tech companies are up to, any artistic subtext to their logos isn't really high on my list of concerns.
What I don't really get about a lot of angry art criticism anyway is that this is the period in time where the largest and most varied quantities of art are being produced,
and a huge amount of historical stock has been digitised and is freely available.
People could be browsing these online libraries of paintings they say they would enjoy, and that they feel angry are not being celebrated.
Instead there is a debate about whether facebook's advertising is too abstracted.
Here is an online link to the digitised painting collections of the UK's National Gallery:
You can look at high-resolution scans of Diego Valesquez or John Constable's work for free.