1st line might not be as great as last season but the 2nd line is what's sinking the Jets right now, one can argue that the 2nd line's struggles have put additional pressure on the top line and the Lowry line esp at home where they are getting heavily sheltered. The team is night and day difference between when the 2nd line is on the ice and when it's not.
To illustrate, here's a comparison between stats of 3 versions of the Jets and how they rank across all 31 teams:
Version 1: "Current Jets" as they have played so far this season
Version 2: "2nd Line" Jets i.e what the Jets look like when 2nd line is on the ice (using Patrik's numbers as a proxy for 2nd line)
Version 3: Jets without 2nd line on the ice
As you can see the difference between when the 2nd line is on the ice to when it's not is night and day.
Without the 2nd line on the ice we look like a pretty good team, right up there with the real contenders in these important 5 on 5 metrics.
When the 2nd line is on the ice, we look like a lottery team, only Rangers and Senators have a worse CF%. Only Arizona has worse GF%. No team has worse xGF%.
When you mixin the 2nd line with the rest of the Jets, we are basically a middling team at 5 on 5.
These are disturbing stats. We are basically half way through the season and are no closer to finding an answer to what to do with that 2nd line. We haven't even tried much to fix them other than the Connor/Ehlers switcharoos. These guys play 12-14 minutes a night @ 5v5 so it's not like we can just hide them away like a 4th line. I don't know how we go into the playoffs with a 2nd line that basically has the results equivalent to a lottery team and hope to make any noise.