It's complicated, assessing Tavares. I didn't like what I saw from him in the playoffs, but I've also defended his signing before. I can see both sides of the issue. I don't have the answers.
On the one hand, wind the tape back to 2018 and put yourself in the position of Brendan Shannahan and Kyle Dubas. Here's a big bodied 27 year old center, coming off a point per game season, that goes to the front of the net and brings an extra dimension to your team in addition to some veteran leadership for a young core. He wants to sign: your team is his top choice. It doesn't cost a single draft pick, and you figure you can keep your forward core of Matthews, Marner, Rielly, and Nylander all together.
Toews and Kane were about 26 when they signed their big deals in 2014 (eight year deals, as opposed to Tavares' seven). Kopitar was around 28 when he signed for $10m with Los Angeles (also for eight years). So there was some precedent for giving Tavares the big contract he received, and to his credit, he has remained a roughly PPG player since suiting up in blue and white.
On the other hand and with the benefit of hindsight, those two teams (Blackhawks, Kings) had early success with those big contracts (I think LA's cup run may have actually preceded Kopitar's deal?), but now both clubs struggle just to make the post-season.
I think the signing made sense at the time, and I still think Tavares is an asset. If you take him off the roster, you need to find someone else capable of replacing his production.
But he always leaves you wanting more, doesn't he? He's good for a point per game, but at that cap hit you really hope for somebody who can blow the doors off the barn from time to time (Matthews, Kane) or bring you selke level defense (Toews, Kopitar). Tavares just never looks like an $11m player and that can be frustrating. Furthermore, he's getting to the age where you can reasonably anticipate diminishing returns.
As to whether his cap hit could be better spent elsewhere, that's all speculative at this point and depends on who is available to sign for how much and how long. Let's say Tavares were on an eight million dollar per year deal, does that extra cap space change the trajectory of this team in any material way? I'm honestly not sure.