Yes teams obviously have fears over his durability, and aren't going to give him a longterm deal that he wants based only on how he pitched last year.
I think he got the short term high AAV deal with opt-out he was likely looking for given his market and with a team he had great success with last year.
Rea for 5m is ok for depth given we lost Wesneski/Smyly. From a pitching standpoint the Cubs seem to prefer to buy low-ish on guys with a profile they see with potential for improvements and bet on their MLB pitching infrastructure get more out of them. I also think they see pitching as more risky than hitters due to higher rate of injury as well (if your 30m AAV SP needs TJS you've just lost a 3-4 WAR player for at least 2 years, which is enough to cost you a playoff spot or 2).
Both those factors combined, Hoyer tends not to make huge bets using huge assets (prospects for trade, or money) on elite pitchers at the top of their game. That's why I have doubts they would fork over big prospects, especially position players, for 1 year of Cease/King etc.
They seem more willing to spend more resources on position players since their abilities are far more stable and much less able to be improved, plus are less injury risk.