It's easy to say things like that with hindsight. Choosing Sparks was the right choice at the time, and something every GM would have done. McBackup was not going to repeat his performance, and he was gone to UFA within a year anyway.
It was not 7 years, and using your logic, Campbell would have been "hot garbage" and not worth a shot as well. Same with plenty of other successful goalies (Dreidger, Cup champion Binnington, Cup champion and two-time Vezina winner and Conn Smythe winner Tim Thomas, etc.).
We haven't missed the playoffs any season, and McBackup was a UFA and we wouldn't have had him in 2019-2020 anyway.
Rielly had a career year in points that year primarily because he was healthy, he played with Tavares/Marner a lot, and he had an unsustainable SH% and OISH%. It had nothing to do with Hainsey. Ceci was a better player than 38 year old Hainsey, and he was already locked into either a contract or arbitration.