Honestly, I think you haven't made the case that optometry > dentistry/engineering/anything is because you can't. At the very least, salary stats are on his side. You've already walked back your previous position (only one thing is "semi-legitimate"), to what you just said here.
I believe a lot of what treytrey says. I believe it when he says 23 people applied for one 75K position. Why? Because I've been in hiring and hiree positions in recent times and those numbers are conceivable to me. Does that mean that ALL 75K jobs get 23 applicants? Or that there are no jobs for 100K? No. But do I believe there are ODs out there who have trouble finding work/underemployed/not making ends meet? Hell yeah. Do I believe that employers know they can offer increasingly lower wages because there are increasingly desperate ODs willing to work for less and less? Hell yeah. That's the basic premise of supply and demand and right now, in many places, there's a lot of supply.
A current "expanding" optical chain in Canada (
https://fyidoctors.com/) uses a set formula to assign pay for everyone (owner OD, associate OD, staff) across all their locations in Canada. The pay scale is non-negotiable. You take it or leave it. Associate ODs make 21% of all their billing. I personally don't like to criticize an absolute earnings number, as what you end up taking home will depend on volume, and perhaps the volume will be good. But 21%? How much would you have to work in a day to just make (say) $500 (CDN)? Who wouldn't get burned out by that percentage? Unless every single patient was private pay, buying two pairs of PALs with AR and Transitions, you'd be up to your neck in work just to break a couple hundred bucks. But fyidoctors manages to hire Associate ODs all across Canada. Why? Because they know that even at "just" 21% pay, there are ODs who will still agree to work with them. And why is that? It's because it's a job, and having a job beats not having one.
I recently chatted with an fyiDoc owner looking to hire an associate OD. He had many many inquiries. He singled out the resumes of two individuals, a male and female, for interview. These two docs were incredible. They were the type that you'd hire in a heartbeat, just based on their resume without ever having met them. We are talking legitimate academic, non-academic, professional, and non-professional accolades and excellence in every facet of their lives. And only one of them would get hired. For a job that would pay 21%. True story.
So yes, not everyone has a 100K job to walk into. As aside, once you've been out a few years and get your life going, 100K really isn't that much.