Because so little Cap space?

Well it was self induced. Paying three picks for DeBrincat and not having the cap to resign him possibility. Sens added more cap this year by acquiring Chychrun and resigning Zub.
Wouldn't the Sens been better off having about 13m in cap by not having DeBrincat and Chychrun (sign UFAs) and keeping two first rounders, two second rounders and a third.

Disagree. If DeBrincat were dead weight, maybe. But they will be able to get healthy return for him. They got Zaitsev off the books and have solid prospect pool that are close to NHL ready.

Go look how much cap space is opening up the year after when the buyouts finish. Ottawa is close to an end product . Yes, the youth has to mature.
Just goaltending and depth at forward needs help. Lets pray that the goaltending gods are smiling down on us.