This is something that I always found a little odd. I think most brewers would agree that high tech, professional equipment doesn't equal great beer. Yet that is what is banned at competitions?

I also think that most brewers would agree that it is the competency of the brewer that makes great beer. Maybe they ban using commercial equipment in an attempt to ban/discourage professional brewers?
Commercial equipment can also equal a 10 gallon homebrew setup in a picobrewery. Anything used for commercial purposes. But commercial ingredients too.
I think it's to discourage commercial brewers from trying to market or quality test their beers in competition (which as we already established would be a stupid thing to do anyway), but also to prevent someone from going to a commercial brewer, paying them to produce the beer, and then entering something they only marginally had a hand in actually brewing. Basically brew it on your own gear. I know some comps allow BOP beers, where others expressly prohibit them.
For me, pinning down "the spirit of the competition" is a subjective argument that, while I agree on principle, is shades of gray, as I said earlier.
It's like telling a mechanic or body shop tech, who works in a shop all day, but then goes home and works on his own car (say, refurbing a muscle car) that he can't enter it in an amateur car show because he's a paid tech, vs. telling a commercial shop that they can't enter something. In my mind, one an be both a pro AND a hobbyist, although not a pro and an amateur.
For me, I suppose the line is creative control. At the brewery I'm working for, I have none (and since the gear has literally only been up and running for a short time, I've done zilch actual brewing on it), and it's still a part time occasional thing (most of which has been assembling the brewhouse) until everything is running full force down the line. My job is primarily haul things, clean things, and grain out. Brewing is a side job.
But even though I brew at home, on my gear, with my own recipes, and my process, during my time, as a hobby.
However, if you're talking about the owner, or the head brewer, someone with significant creative control over what happens in a commercial brewhouse (in the case of a nano or pico, essentially everyone involved, but in the case of bigger brewers, it's a very small percentage), then that's a different story. But even then, who am I to tell someone with such passion for brewing that they do it both for a job, and at home, that they're not a hobbyist too?
So what it all boils down to for me, is if the rules say it's ok, it's ok. If the rules say it's not, it's not. And if you don't like it (whether you're a pro wanting to enter, or a homebrewer mad that pros can enter), then tough luck, don't enter, and put on your own competition the way you want.
I'll agree that it can be kind of odd and annoying to have pro brewers entering homebrew comps to test their product (as I said, I've seen it happen), but if someone's genuinely brewing at home for their own purposes, then their entries are as allowable as anyone else's as long as the rules don't say otherwise. As for me, I may or may not keep entering the occasional comp, but I have zero shame in doing so, because like I said this is still my beers brewed by me as a hobby, completely separate from what is essentially a factory job that also happens to involve brewing beer.