We're there with you!
Just know that this is not your fault only Thumbtack's. They've created a new system where it is benefitial for their company but not the pros giving money to their new system. There are leads here and there, but to your point- not how it was before. Either that, or their marketing is completely off.
I turn on "targetting" only intermitantly... I would say my track record is about three tire kickers for one solid lead, and with leads in my category now costing up to $14.00, I'm pretty much breaking even. In my own case, (resume writing), I am competing with providers from all over the country, not just in my local market. As near as I can tell, most of my local competition gave up a long time ago on Thumbtack.
Ways Thumbtack could fix this.
1) Restrict bids to ONLY local providers
2) Reduce cost of bids to something reasonable, like $5.00 a lead.
3) Only charge the lead if the Pro is hired.