I'd say you're wrong about Zucc. He didn't have top quality linemates when he played for the Rangers. Once he was traded to the Stars, and had Benn and Seguin as linemates, he became close to a ppg player. Only had a playoff run with them, but 11 points in 13 games. Zucc can play well without Kaprizov.
Most players will have better production with skilled linemates, so just looking at points in the past doesn't really give us a correct description.
Boldy + Hartman, Steel, or Freddy G isn't better than what Zucc had for linemates in NYR. So I think it's a pretty apples to apples comparison.
Zucc is like Granlund, he was always going to produce better with goal scorers. That's something he didn't have a ton of with the NYR.
Hartman was never put in a top 6 role prior to the playoffs against Vegas. He can absolutely be a top 6 player. I don't care what your math says. Players can produce more when given more opportunities.
Also, you have no reasonable logic to prove that this team without Kap would only win 2 in 10 games. That's .200 win percentage. This team without Kap is worse than Chicago? Worse than Arizona? Worse than Columbus?
Steel + Kap (4.25 gf/60, 3.4 xgf/60) is at a similar pace to Hartman + Kap (4.45 gf/60, 2.7 xgf/60) last year. Rask + Kap had (3.08, 1.89 xgf/60) 2 years ago. Rask and Steel are/were fringe NHL players.
It took Hartman 5 games to play himself off the Kap/Zucc line at the start of the season. Or did we all forget the 1-3-1 start to the season.
This team has played:
-12 games against good teams (.556 on pace for a 90p+ season) 4-7-1, 2 regulation wins.
-13 games against bad teams (.500 or worse). 11-1-1 record, 8 regulation wins.
-6 games against fringe teams (in between the other 2). 3-3-0, 3 regulation wins.
The team without Kap on the ice has 34 5v5 goals (1.09gf/game). I don't even know if they would have a functional PP without Kap. Foligno, Greenway, Hartman, Steel, Spurgeon, Dumba or Freddy G on PP1 instead of Kap just seems like a trainwreck.
So yes, I think this team is as bad without Kap as PHI and VAN are fighting for a bottom-5/6 spot in the league. They might get to OT, but I don't see them winning many OTs or SOs without Kap. It's really no different than the past Wild when Gabby was in and out of the lineup.