Neil Paine is very good, but essentially, no. CARMELO is not especially well regarded in the analytics community. A lot of the issues stem from somewhat strange decisions that 538 has made to use a k-nearest neighbors model for their player projections, which results in throwing out the bulk of the data, and force-fitting players onto their nearest comps, even if those comps are not particularly close. A striking example is Zion's 5-year projection, which has improving rapidly, and then declining somewhat inexplicably in 2023 and 2024, before improving again, etc...
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This sort of bounciness is indicative of an overfit, and appears to be caused by the fact that Zion doesn't have many close comps, but two of the players they're fitting Zion onto are Beasley and Blake Griffin, who both had brief declines a few years into their careers. This is a somewhat obvious example, but the issue is endemic to any player without a lot of great comps, which includes essentially all rookies. (
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Additionally, the weighting of the metrics they've chosen are arbitrary (1/3 BPM; 2/3 RPM), which is always a bad sign.
CARMELO has performed well in the the ABPR projection contest the last couple years, that's not a long-run player projection contest, and isn't really germane here. As someone who has also performed very well in that contest, I can tell you the secret is mostly in getting your minutes projections correct (e.g., will Kanter play 15 MPG or 30 or will Kawhi play 55 games or will he play 70), how tightly you regress teams to the mean (e.g., will any team project to win fewer than like 24 games), and how you handle projections of players not yet on team rosters (e.g., the much maligned replacement level). 538 may very well do these things quite well - I don't know, but again, they're not super germane to player projections.