Dude brought the Knicks to 2 Finals trips. You can argue that he wasn't putting up the same numbers in 1999 but he was old; superstars centers from his era like The Dream and The Admiral were also pretty much busted by 1999.
In the 1994 run, the Knicks could had won the title if not for that Hakeem block and John Starks playing horribly overall. Yes, Ewing shot the ball horribly at .363 (raw), but he was never acclaimed as an offensive superstar anyway. He was always known to be a defensive beast. Hakeem averaged 9.1 rebounds and 3.9 blocks while Ewing 12.4 and 4.3. I'm not saying that Ewing played better than Hakeem; just that defensively, Ewing was still pulling his weight.
The Bulls acknowledged that the Knicks were their nemesis and the toughest nuts to crack in their title runs. Not anyone else, but the Knicks that were led by Ewing. Obviously there is no pity trophy for runner-ups, but there can only be one winning team and basketball is also a team sport; no matter how good Ewing was, he still need his teammates to be good enough.
I feel like he is both underappreciated and overrated.
He is unappreciated in the sense that because he wasn't a champ, or an MVP, most newer fans don't really remember him or mention his name in the conversation with all time great centers. Like whenever a Philly or a Denver fan tries to put Embiid and Jokic in the great centres convo, they go straight to Wilt, Shaq, Hakeem, Kareem, Bill Russell, etc. And just skip over guys like Moses Malone, Robinson, Ewing, who even if you think Joker or Embiid are better, should at least be in the discussion.
At the same time, I feel like he was also overrated because his college career was so great and he played in New York. He was constantly compared with his contemporaries like Hakeem, Shaq and David Robinson, but he was really a tier below them. I feel like his offense especially was overrated for the fact that he didn't have another elite scorer alongside him for his prime, and wasn't great in the clutch. But his defense was elite.