What has haunted this team is the absolute inability to: 1) draft the right QB in the NFL Draft; and 2) put the right people around the QB they do draft.
The last QB the Browns were successful drafting came out of the 1985 Supplemental Draft. Think back to how old you were when this happened. I was 21. The very next off-season, the Browns hired OC - Lindy Infante. They went from 8-8 behind Mack and Byner rushing for over 1000 yards apiece in 1985 to 12-4 with RBs combining for 117 receptions (Mack 28, Dickey 10, Byner 37, Fontenot 47) in 1986. Knowing defenses were chomping at the bits to stop Mack and Byner and blitz the cement shoed Kosar in year 2 - Infante chose to dictate the weekly chess matches. You want to zone blitz us? Ok, here's a little Herman Fontenot and Brian Brennan combining for 102 receptions almost exclusively on 3rd downs. Meanwhile, Byner and Mack could just as easily catch swing passes to the flats (which was fun to watch when that area of the defense was vacated by the designated zone blitzer). Talk about making life EASIER for a 2nd year QB - this was the best I've seen this team do in my lifetime.
When Jim Harbaugh went to play QB for the Colts, he credited Infante for being the best offensive coach he had tapping what he does best. I read an article where Harbaugh said he brought a lot of what Infante taught him to use with QBs he coached. He combined that with what he learned from other coaches but emphasized Infante's main principles for QBs eased and expedited the progressions.
All that to say, coaching has a profound impact on how well a QB develops as well as who you have protecting them. Watson is only going to turn 28 this year. QBs like Kurt Warner, Steve Young and Doug Williams didn't play their best football until after they were 28 years old. Rich Gannon, Brad Johnson, Fran Tarkenton and Jim Plunkett are other QBs that found more success in their later 20s/early 30s. I think I already shared in a previous thread the dreadful Terry Bradshaw's stats over his first 5-6 years he played; and got benched for guys like Terry Hanratty and Joe Gilliam. Sometimes it's needing more surrounding talent - other times it's the luck of having the right offensive mind assessing how to tweak his offense around the QB. The opposite of that is the square peg/round hole you alluded. FWIW, losing a 1st and 2nd string RT + whatever we continue to settle for at LT can lead to watching 5 different guys start at QB in 1 season. Any QB that confuses what he's here to do with thinking he's Larry Csonka initiating contact with LBers and DL - needs to be BENCHED by coaches or inevitable injury will do it for them. Coaching matters so it's a little disturbing to see them waiting until after Watson completed his 1st year here to start planning for the right system and adding coaches. Clemson and Houston were ready for Watson - can we honestly say the Browns were too?