Positivity is hard to sustain when things aren't going well and negativity is hard to sustain when things are. It's hard to sustain a break from the reality (as one sees it).
Now, the question is--are things going poorly? That's a lot harder to answer, because fan perception is driven by expectations and sports fan expectations have, in my view, amped up over the decades into "contend for a championship or the team is a bunch of losers." I think the internet has played a large part in that, as internet culture in general has led to one-upsmanship. You can see this, e.g., in comments on an article about an accused murder/rapist/pedophile, where people will fall all over themselves to prove that they'd punish the person the most brutally. In sports fandom, this manifests as ever more extreme expectations, IMO.
Honestly, I thought the last couple of seasons were fun even if I knew they weren't title contenders. Well, the second halves were fun. Over the years, I've tried to pump the brakes on the "I'm only enjoying sports if my favorite team is a serious title contender" mindset because that's a ticket to rarely enjoying your fandom.