Totally agree, we haven't really had capitalism for most of my life. It is possible though, and most of US history included at least mostly free markets.

I was a software consultant for many years. I'd put that on the list of truly competitive marketplaces. People were either willing to pay me to do a job or they weren't, and I would have to adjust my prices and terms to try to increase or decrease my workload.

That’s one, and I suppose marketing firms to some extent also fit.

But these are small niches that don’t make a whole sector, and arguably it’s on the fringes comparatively to everything else

Broadly speaking the so called free market is only in its name

For sure, I'd argue that's mainly because any industry that centralizes or grows big enough to really matter finds itself the subject of new government oversight and regulation. As soon as the government becomes involved, for better or worse, its no longer a free market.