My 2009 MBP shipped with Leopard and I upgraded it to Snow Leopard within a few months. It was on there for a couple years.
My first computer was a Mac LC in 1991, and I was a die-hard Macintosh fan all throughout adolescence. I learned to program with Think Pascal on a Centris 660AV. My whole family continued to use Macs after I gave them up in 1998, so I certainly used them during that decade, I just didn't like using them.
I wasn't talking about the 90s (And I don't think any mac fans complaining about the dropoff in quality are talking about pre-OSX Macs either, other than Siracusa and the Finder). You basically missed the entire era where OSX was really good on its own, improving rapidly, and next-generation when compared to the competition in Windows and Linux. This period was basically (Again, according to the mac fans complaining about Apple's declining software) bookended by Panther and Snow Leopard, so you essentially came in right towards the end.
To be honest, I can only think of 1 feature that was added post-Snow Leopard that I use regularly. Being able to receive/send messages from my mac and that isn't available to non-iPhone users. And better trackpad gestures, but that's closer to hardware (although it requires OS support) than software.
My first computer was a Mac LC in 1991, and I was a die-hard Macintosh fan all throughout adolescence. I learned to program with Think Pascal on a Centris 660AV. My whole family continued to use Macs after I gave them up in 1998, so I certainly used them during that decade, I just didn't like using them.