I don't know if you've noticed, but car classifieds sites blow pretty big chunks. In thinking back on it, I almost have begun to wonder if the explosion in car auction sites has less to do with taking away the horsepower of the big guns like Mecum and Barrett-Jackson and more to do with simply taking advantage of how poorly built most classifieds sites are.
If you spend any amount of time (as I do) looking for certain cars and trucks, mostly of the enthusiast type, you'll quickly find you don't have many choices anymore beyond craigslist, Bring A Trailer, and Facebook Marketplace. Sure, there are legions of other websites, but most all of them are rarely updated or completely overrun by other websites posing as digital brokers.
Right now, I'm looking for a 1998 Aston Martin DB7 coupe. If you use Autotrader, the same 5 cars pop up, over and over again. I'm guessing 4 of the 5 are no longer even actually for sale. And on top of that, the Autotrader site has nominal information that really does cater to dealerships that rely on providing nominal bits of information.
On top of that, most leads from Autotrader go no where. When I was hunting for an 80-Series Land Cruiser, I emailed the same seller within hours of his listing going live upwards of 12 times and he never responded. Of course, then you find out that Autotrader sometimes takes over a week to post a listing, at which time the same vehicle may have already been sold locally on craigslist. The real kick in the teeth is that seller pay for the privilege of listing their car on Autotrader!
It's clear it is time for car classifieds sites to be reinvented with the enthusiast in mind, taking a page from what the popular auction sites do well (presentation, seller involvement, etc.) and give owners and buyers of enthusiast vehicles another choice.