I was rejected by YC several years ago -- on two separate occasions.

While I was a little bit miffed, especially after the second time (you know that old "fool me once, shame on you, fool me twice, shame on me" expression), I eventually gained a greater understanding which led to me not being unhappy at all...

Let me give you that greater understanding here, in as little space as I can...

First, let's understand that the relevant place to accomplish something, technology-wise, historically changes as the years do.

To understand this, consider the following. Let's say you were a programmer in the past, and you wanted to work with the highest technology available in a certain year.

If you lived in 1999, your choice for a company to work for would have been Google.

If you lived in 1975, your choice for a company to work for would have been the newly founded Microsoft.

Before 1975, you would have probably worked for Digital Equipment Corporation, Xerox Parc, Bell Labs, IBM, in that order, as the years got earlier -- those would have been the places to be.

In other words, you can think of 1999's Google -- as 1975's Microsoft.

Now, applied to Y Combinator:

You see, when I applied to YC, I did so (if I recall correctly!) around 2015 or so, which was at least 10 years after 2005 -- the point in time at which Paul Graham had founded YC.

Why is that important?

You see, I wasn't looking for 2015's YC.

I was looking for 2005's YC.

That is, I was looking for what Paul Graham was in 2005:
A non-institutionalized investor who would invest small (~$10K) amounts of money over a short period of time (3 months of summer), with a small bunch of teams equally being invested in, and with whom (and with the people on the teams) you could have a friendship relationship with, over dinners every week...

But, those days, due mostly to YC's continued practically exponential growth -- were long gone by 2015, by the time I applied.

Now... here's the wisdom of all of this...

You see, 2005's YC -- while it is lost to present-day YC, it is not lost to the world.

It has merely changed places... and names...

Much like 1975's Microsoft shifted to 1999's Google...

You see, what you are looking for (what I was looking for), is a small-money investor that you could have a friendship relationship with.

And guess what?

These days, they exist all over the Bay Area (well, all over the world, but in the Bay Area in particular!). They're called "Angel Investors" (although, all are not the same -- you'd want one as smart as Paul Graham -- but they're out there!).

Or... you could do the equivalent of what students do when they apply to Harvard... which is to apply to present-day Y Combinator.

Keep in mind, with respect to Harvard, there are a lot of other prospective applicants -- so the bar is set very high. YC, in its present incarnation, is not very different from this.

My guess, and it's only a guess, as to why you got rejected from YC is simply this:

-Your app or product doesn't have enough user traction/revenue (compared to the other applicants), which might have to be very high indeed...

How do I guess this?

You see, as investment companies choose companies and make money from their investments -- they get more well known. As a result of becoming more well known, more prospective investees apply to them. So they become more selective, more choosy.

This cycle continues until they are what can be considered "elite".

(I love that name "elite", it also applies to schools too!)

But, when you do business with an "elite" organization -- you had better be "elite" as well... or to quote the Soup Nazi on Seinfeld "No soup (deal) for you! Come back (try again in 1 year!)" <g> (Don't try again in 1 year -- for most people (without fast user growth) it's a losing proposition they will fail at!)

All investment companies, as they become more elite look for one thing and one thing alone -- user traction, and growth of the user base, specifically the speed of the growth of the user base over time...

Basically it's a popularity contest.

If your app isn't popular... and more popular than the apps of the other people applying -- then you aren't "in".

Advice: Seek 2005's Paul Graham.

Stay away from Y Combinator (even though I love HN and Paul's essays!) because it's institutionalized, and in maybe 10-20 years, it will replace/supplant VC firms...

All investment firms, if they are even moderately successful, move towards VC, and eventually eventually (if they aren't stopped by economic downturn, war, famine, etc.) move to private equity...

That's the cycle.

Find the equivalent of 2005's Paul Graham!

Good luck!

Also, you can write me at peter.d.sherman@gmail.com -- if you want to discuss this further...