AOL didn't lack depth: they literally had email (@aol.com), social media (AIM), video-calling (Vonage), cloud filesharing (Xdrive) and so much more.
Ultimately, they failed because (1) they were overvalued to begin with and (2) had a bad innovation model (top-down) that led them to (a) over-commit to online ads and (b) under-commit to broadband.
Google is sustainable & mature, and it has a distributed innovation model that will avoid the particular mistakes of AOL.
Google is reacting to the Walled Garden trend, not driving it.