Ozzie's not dumb. You acknowledge that he very well may have known what he was signing (I would argue it's almost a given that he did). Even if the agent is bad and was acting in their own interests more than Ozzie's, he is free at any point to cut them loose. He seems to be very happy with the deal he signed. We can all look at it and say that he left a bunch of money on the table, but we don't know exactly what his considerations are; they certainly seem to be about more than just getting the most possible dollars.
I would argue, based on the option years, he has a bad agent. He should rectify that for himself. But was he taken advantage of? I have no idea and would guess that he wasn't. Again, if he felt like the agent was working in bad faith or wasn't getting the most he could, he could break that relationship at any point and get a new one.
Acuna and Albies seem perfectly happy, and they're both going to make a lot of money...yet you have a bunch of dudes who know nothing about them trying to protect them...from what? They are adults in full control of their own situations. They made a decision.