Earlier quoted context omitted.
My personal understanding is that Thumbtack only wants candidates with Ivy League educations, and that they're dismissive of everyone else. I have heard they have difficulty filling their positions due to this. Is that accurate?
I can confirm. They have a very smug and elitist attitude. They also engage in some pretty shady business practices (just google them).
I googled for "thumbtack shady business practices." The top results were professionals complaining about 1)inability to buy a single lead at a time, and 2)bogus leads. The first is specifically a measure to filter for more dedicated businesses; regarding the second, there are multiple engineers and manual reviewers filtering out bogus leads and from what I can tell they do a solid job.
Since you're likely coming from a technical pov, you may also consider the fact that our company gets a considerable fraction of traffic from SEO to be shady. I agree that gaming SEO by itself is a silly thing to do. Fortunately for me, optimizing for SEO is somewhat correlated to optimizing for quality content. Additionally, at our company's current growth stage SEO is becoming somewhat less important than building a solid product; this likewise makes me optimistic.