The Rangers have been a bad team for much of this year, but the OP is way off on a lot of details about why imo.
First of all, saying any of these guys "can't defend" is misguided, it'd be more accurate to say that they look bad in this man defense system, which they absolutely do. Take Girardi for example - was horrendous under AV playing man, now is pretty passable if not more in TB playing a simpler system and getting the minutes he should. I firmly believe that NYR needs to fire AV and get a simpler defensive system that actually plays to what they have before any serious judgements about any d-man can be made.
For the offense, offenses with many if not most of the same players have taken NYR to the finals and the the ECF. To say they don't have the pieces to have a good offense is misguided imo. A good example of how this estimation is off is in the idea that Zucc would be the Isles' 4th or 5th best forward. Taking a team having a hot season and a single player from a team having a cold season is a setup for a poor comparison. If you go back to the last full year everyone played, Zucc outscored every single player on the Isles except Tavares who beat him by 7. Compare Zucc to a guy like Bailey who I assume is one of those 3 or 4 players OP thinks is superior to Zucc - Bailey, who is 28, is now having his first season where he is superior to Zucc in scoring. Is it accurate to say Bailey all of a sudden at 28 years old has become a consistent 65-70ish point player he'll be this year, or to say this year he's having a great year and he's really more like the 40-50ish point player he's been for the previous nine seasons including the years that are typically peak scoring years for NHL forwards?
NYR forwards are always, always, underrated on here for whatever reason. Look at how much guys like Zucc or Kreider scored last year, then look at who they're ahead of or even with - the other guys are players people on here absolutely fawn over while Zucc and Kreider "not good enough to be main pieces" or some such garbage.
NYR are bad this year, but the sweeping conclusions about many of the players are way off imo. They need a new coach as badly as any team ever has. You can argue that AV is or isn't or was or wasn't good all day, but the fact is at this point he's absolutely outlasted his peak with NYR and it's absolutely time for someone new.