To answer OP question, here are my thoughts:
So many appraisers have joined AMC panels, where the pressure to produce necessarily impacts work product. Not condoning them, they still sign, but we are all human (well most of us). It gets harder to 'dot every i' when you have 4 to complete by the weekend.
The other issue is that as the industry continues to allow things like runners, not inspecting comps, tons of boilerplate, etc to run rampant, it becomes increasingly hard for the one off truly independent appraiser to compete with that. So one by one, each res. mort. appraiser has to decide " can I compete with my ethics and report quality at this price point, or do I hang it up?"
I think the abundant workflow in recent years (certainly not anymore) also impacted quality in a bad way, moreso than any fee. When tons of possible work was coming in, some appraisers wanted it all. The only way to get it was to cut more and more corners...but alas, the reports continued to be accepted. Nice they all thought, lets push it a little more.
We talk about supply and demand a lot, I think that can be applied to appraisal report quality as well. If there is no DEMAND for good, well-written and supported reports, then the SUPPLY of them will necessarily decrease as a result.
The imminent saturation of the industry with PAREA grads, hybrids, etc, will only exacerbate the issue, IMHO.
I have entered what I think will be my final countdown for reports. I am thinking March or so will be it, unless something big time changes in my life. I will miss what it was, but not what it has become.