What do you see as net negative about it? I’m familiar with the product but not that aware of how it’s been used.
Mechanical Turk was one of the early entrants into "how can we rebrand outsourcing low skill labor to impoverished people and pay them the absolute bare minimum as the gig economy".
I think this is a very first-world oriented take. It efficiently distributed low-value workloads to people who were willing to do it for the pay provided. The market was efficient, and the wages were clearly on par with those who were doing the work found economical to do, considering they did (and still do) the work for the wages provided.
The gig economy was very much a net positive here. Some people used it to quit factory work and make twice the income; some used it as negotiation terms against the more tyrannical factories. Factories were sometimes a closed ecosystem here - factory workers would live in hostels, eat the free factory food or the cheap street food that cropped up near the area. They'd meet and marry other factory workers, have kids, who'd also work there. They were a modern little serfdom. Same goes for plantations.
Things like gig work and mturk were an exit from that. Not always leaving an unhappy or dangerous life, but making their own life.
If it paid badly, just don't work there. These things push wages down for this kind of work, but this work probably shouldn't be done in service economies anyway.
The conditions you're describing were caused by the systemic globalist status quo that Mturk is a part of; Mturk did not fix that, it perpetuated it.
This paragraph is so tantalizingly close to putting its finger on the issue. The fact that a company found someone willing to do a job for what they want to pay does not mean that it's ethical or moral for them to do so.
In this case (as in many others), one of the predicates was finding groups of people whose existing options, financial literacy, living conditions, or some combination of the three were already so bad that becoming digital serfs was a minor step up.