The Islanders as constructed cannot compete with the best teams in the league. Just because we have elite goaltending does not mean we need to overpay bottom line players and miscast them in roles they cannot succeed in. These are unforced errors. Nobody made Lou trade for JGP, Palmieri, and give them contracts that didn't make sense. Also, your point about analytics is correct. They are data points. However, by whichever metric you use, this Islander team gets out chanced mostly every night. That is not sustainable. Metrics don't have to tell you that the Isles don't have high end players who can create consistently outside of Barzal.
You can point to the ECF x 2, and call it a success. To me, it is not enough. The team surprised many and outperformed their expectations twice. Instead of building on that, we didn't do enough to get better each year. Most teams strive to get better each year on paper (Vegas is the most extreme example). The Isles do nothing significant. They just watch their players age, give away first round picks for replacement level players, and then hope goaltending wills their way into a playoff spot. That is not sustainable. They can still play with heart and acquire players with skill. Not players like Palmieri, JGP, and Romanov. To your point on Romanov, he's at 45% xGF and 50% actual GF. He doesn't create anything offensively. He's an average passer. There is nothing in his skill set that screams top 4 defenseman. He may become one some day, but doesn't look likely based on his skill set. He's good at blocking shots. Not worth a 13th overall pick. He's 22 so I guess there's hope.
Overall, Lou fell in love so hard that he refused to make this team better each year. So instead of using cap space as an asset and potentially signing a JG, all we have are players like Bailey, JGP, Palmieri, Romanov, etc. It's infuriating.