Regular college students are increasingly being offered a similar option. College loans that gets repaid out of future earnings only.
I disagree that it is exploitative, because it is a scenario where both parties have their goals aligned. The player makes more money if they make more money, and the investor makes more money if the player makes more money.
Obviously, there is a percentage that starts becoming actually exploitative, and there should be clauses to protect both parties like all contracts. Those players with the highest of pedigrees should likely be able to negotiate a cap on the return. But I truly see nothing wrong with the business model. Nobody is forced to take the deal, although in baseball due to the meager salaries in minor leagues, it's certainly more necessary (college basketball players get treated like royalty in comparison). It's similar in fact to the loans and advances for training that agents give to prospects before the draft in hopes they sign them... whereupon they get a % of the future contract.
In the case of Tatis, the article literally mentions that he was able to functionally improve his training and life while working his way to the majors. He may not have become the player he is without that money. And he made significantly more money than expected, much more than the 10% cost him, so he's ahead in the end.