About 6 years ago, before Weebly came out, I was working on an open source drag-and-drop (user-friendly) content management system - I had spent 2 years on it (all my spare time) - I intended to offer it as a service eventually. Then I found out about Weebly (who got funded by YCombinator) - They had a huge well-funded team and so they were able to quickly develop a great product and they got massive traction. To be fair there were other competitors in the space, but they also had lots of funding - I decided that without funding, I could not compete with these products (in that space) and I so ended up just giving up my 2 year project.
Then I started working on a new open source project (3 years ago); in the area of realtime data; my plan was to build a tool which would improve how data is transferred between the database and the frontend client. Unlike my last attempt, this time, my open source project got a lot of traction; I later found out about Meteor (YC), then later Firebase (YC)... I'm still working on this new open source project though; I have decided to keep working on it forever (or until it becomes completely outdated) I intend to turn it into a service - I feel that no matter what I do, some great company will come out of YC to make all my work economically meaningless so I might as well keep going.
Basically YC is just churning out competition and putting huge amounts of money behind them. It's taking opportunities away from the poor, hard working engineers and giving them to the few lucky ones who happen to be selected by YC.
It's not just YC though, it's VC in general; the huge amount of funding that they give out creates an artificial barrier of entry for newcomers.
Basically the idea is that if you don't have a good social network, you cannot raise funding and if you cannot raise funding, you cannot succeed. If VC funding didn't exist, the system would be a lot fairer.
I think YC does select good founders, but they miss a lot of really good ones too and these suffer greatly.
If you're an investor, you should be mindful that for every investment you make, you're probably hurting someone else somewhere in the world - So make sure you're investing in the best of people (not just your friends).