The hardest part of startups is probably the making good decisions part. To be a good VC you need to be better at founders at judging startup decisions, AND you need to be good at LP deal flow AND you need to be good at startup deal flow. LP deal flow has to come first (otherwise there is no fund), and because of zirp a lot of VCs got funds up without good startup deal flow or the ability to judge startups well.
In other words it's hard to be good a VC too, but for a while it was artificially easy to be a bad VC.