I don't know if it's a popular opinion to hold but YC has always been a kingmaker from the start. Only when Dropbox filed an IPO and is now worth a bazzilion dollars in the public market most of the media has caught up to their work. To the entire team at YC keep going there are phenomenal startups to come :)
In my opinion YC had some good wins early on but now, especially as the cohorts have gotten much larger, it’s not clear if they’re still “kingmakers”. It would be more impressive if their cohorts were still very small and had a high success rate (however you measure success).
The key factor here is the time it takes for a startup to be "successful", it took 9-11 years for Dropbox, Airbnb, Stripe to get to where they are today after they went through YC. It will take a similar amount of time to see how successful the larger batches are. I'm guessing your concern is whether they manage to give the same attention to each of the startups as the intake size increases. PG talks about doing things that don't scale (http://paulgraham.com/ds.html), so I'm guessing YC is trying to experiment with scaling, and it will be at least a few years to see definitive results.
