Another factor is that some places a great season last year, many other places had a "bust". Nothing gets buyers excited like having a couple good snow seasons. My dealer is still selling every SxS, ATV and Slingshot he can get his hands on.
I think you've forgotten about the adventures with the Ducati ignition stuff Polaris used in the late 90's and early 00's. Then there were the broken exhaust valves and crank issues in the big block twins. True that the 500/600 domestic engines were pretty bulletproof. I think that overall the new stuff is more reliable and less troublesome. I've routinely put 8-10K miles on each of the sleds I've owned since '09. On those older sleds back in the day, put on that many miles and you would have the chassis falling apart, the engine needing a full rebuild, etc. Yes, I've had to do some repairs on my newer stuff and one in particular had a couple trips back to the dealer (under warranty) to deal with a jackshaft bearing. For the rest of them, it was basically planned maintenance and taking care of the "known" items that need to be done around a certain number of miles. Now that isn't to say that there aren't some "problem child" new sleds out there. Modern stuff has gotten complex enough that sometimes dealers (and others) have trouble fixing them when something goes wrong. Could say the same about modern cars and trucks too.