There's only two ways to get unbound gems at the moment, one is to buy eternal legendary crests and the other is to craft them. You're pretty limited in how many you can craft because of stop gaps in the system preventing you from grinding. Legendary crests which are strung out through a few of the battle pass systems and F2P systems don't award you with unbound legendary gems. So the youtube video that people are referencing are half wrong, but I still think eternal legendary crests are a pretty sneaky mechanism.
Whether you think some of the MTX is too predatory or not is your decision. I haven't spent a dime. What I do think is particularly unfair in an ARPG are soft caps and/or hard caps strung out throughout the game to impede progress. ARPGs historically are about grinding and preventing you from doing this very activity is sort of stupid IMO. It would be like if Diablo 2 told you that you can only run each act boss 10x a day before drop rates were diminished pushing you towards something else, or hard capped to where they just no longer drop loot.
I think if they went about removing all of the caps in the game (soft and hard caps), and perhaps being a bit less stingy of legendary crests you would cease to see so much complaining.