While I understand the sentiment, Marner walking for nothing is probably worst case scenario considering where we are.
Even a subpar trade that nets you SOME return, is more beneficial than that. I'd even consider a short term extension.
You might lose Marner, but then you also lose someone who is capable of putting up 100 points, playing in all situations, etc. I understand his playoff lack of success is defining here, but losing him for nothing potentially harms "the whole cruise control into the playoffs every year" thing they have going on currenty
I'm not saying cap space isn't valuable, but I am saying creating that big of a hole in the lineup and needing to fill it with multiple different pieces, is very hard to get right - and no, I don't think we were another Domi, McCabe, Benoit, or Dewar away from getting it done.