Yep... he's still only 24 years old and he has a valuable, important skill (ability to shoot beyond the arc well). If he bulks up (as most 24 year-olds tend to do) and learns the game more (as players in the NBA tend to do) then he can be a solid rotation player, at least.
Remember: this is a guy who shot 1 of 12 from college three pointers in his two years in the NCAAs and 3 for 13 from three point range in his first two NBA seasons. He obviously has been willing to put in the work to improve his perimeter game and while he might plateau there, it seems unlikely. And I think that with this contract the team could survive even if he did just level off for the next four years.
The cap will continue to go up It jumped over $24 million this year and is expected to jump by another $10 - $16 million next year. So, $10 million in the present market won't look like so much four years from now.
That's the weird thing about the current CBA. The cap can go WAY up, but the exceptions don't. They were etched in stone when the last CBA was signed. The MLE used to be used to sign a 4th, or 5th starter, or at worst, a solid 6th man type player. Now, with 8th and 9th men getting $10+ million a year, the exceptions are practically worthless. In the last 6 years, the non-taxpayer MLE has only gone from $5.000 million to $5.628 million. During that same span, the salary cap has gone from $58 million to $94 million. The other exceptions (taxpayer MLE, Room MLE, Bi-annual Exception, etc. have also seen similar minuscule increases.
Hopefully, this will be corrected in the next CBA. When the cap goes up, the exceptions should go up by a comparable percentage to keep them equally relevant.
In any case, while Meyers didn't sign for the MLE, his $10 million per year will eventually be seen in the same light, even less, than what players used to get when they signed for the MLE.
And, as you say, he's still young and has the potential and work habits to continue to improve. I'm not claiming he's underpaid, but this contract is not an albatross. It reflects current market value and as the salary cap continues to increase it will, most likely, be considered below market and a good value moving forward.
BNM