This is a smart move IMO. I think that social networks were over-valued to such an extent that functionality was often sacrificed. Google does services well, and social does not mix well with every service.
As a long time youtube community member, good riddance to bad rubbish. Their excuse of attaching your G+ profile to your comments did nothing to improve the vitriol that appears there, and it also ended up messing with the brand of a lot of mid-to-high-tier youtubers, killing a lot of revenue.