You're right. That's doing a great disservice to Isiah Thomas.
Please, this kind of stuff is exactly why you shouldn't talk about basketball ever again. Melo's production so far in this relatively anemic scoring era is 24.4 PP36, that's worth 26.75 PP36 adjusted for Thomas' era, and the
best Thomas ever achieved (in one season in his own era, mind you) was 21 PP36, with his career average being 19.1.
Not satisfied? Me neither, let's adjust for usage: Thomas' career usage rate is 25.3%, over which he put up an ORtg of 106, Melo's usage is 31.1% with a 107 ORtg. Let's take a hypothetical Melo and reduce him down to Thomas' career usage and see what we can reasonably expect his ORtg to be. The answer? 114. What about Thomas? If we expand his usage to that rate that Melo is at for his career, we can expect to see his ORtg drop to around 98. This isn't meant to say that had Thomas increased his workload he
definitely would have fallen off the efficiency cliff, but just to illustrate that Thomas wasn't even more efficient than Melo when he finished a drastically lower percentage of his team's possessions compared to Carmelo! Carmelo is the more efficient scorer and by far the better volume scorer, all playing in an era where scoring is much harder to find than it was in Thomas' day. Melo wins, hands down.