While I agree that it sucks these players don't get paid for being the national spotlight, I have a hard time convincing myself that student athletes should be paid for what they do. Should they all make the same amount of money? Should schools get to decide how much to pay each player, a free agency of sorts for high schoolers? Do we then need a CBA for the NCAA too? How much should school get to spend on their roster?
The NCAA can get away with not paying the kids because this is their best option: showcase their talent on the national stage for a year before making the jump to the NBA and earn their millions. To most of the kids, this beats going to Europe or China for a year to make money, where they get less focused on by the American media, have to live abroad (which is a bad excuse to me), might not even get many minutes in a foreign pro league etc. In the NCAA, the top prospects can look amazing dominating their competition even though they might not be that good in the NBA (read: Andrew Wiggins) because the gap is that wide.
Should the NBA lower the age requirement to 18 so top prospects can jump straight to the league? I don't have an issue with this idea, but I would want the kids to seriously consider the cons of doing this and only decide to do so once they're ready to accept any possible consequences. Like I mentioned above, some of the top-rated college prospects we've seen just haven't been great, and they had a year of playing in college before making the leap. Going straight from high school would be an even bigger jump, and only few have had success. Physically, the NBA is a lot more demanding than the NCAA, and again, only a handful of players are likely to have the physicality and body ready for the jump. One major injury is all it takes for their careers to end (or at least take a huge detour) before it even started. It looks like Adam Silver is prepared for any backlash though, even if they may be unfairly attributed to him.
The G League option is one I think could work. They won't be making a ridiculous amount of money, but it's still something and gives them a nice taste of what's to come. It could help expand the G League, too. That said, I can't see too many prospects taking this option because playing against tougher competition than in the G League could hurt their draft stock.
At the end of the day, I think the NCAA is still the best option for the top prospects just because of the coverage they get and they'd look a lot better dominating competition like Zion has been doing, rather than playing in a serious pro league which could hurt their stock.