It actually is a hot take. Maybe you end up being right .But he is not always injured. He pitched over 200 innings last year and faced the most batters in the AL. His ERA was a pretty good for the AL 3.74. His WHIP was 1.314 which is a little high for him but not terrible at all. 2019 will be his age 31 season.
I also wouldn't go so far as to say GM's are in agreement with you. More than likely his contract demands were too high and he hasn't lowered then enough.
As recently as 2017 he made the All Star team but he did pitch only 145.2 innings which as his lowest amount since his rookie year so obviously not always injured.
His projections for this year are also pretty good . If he gets a minor league deal it will pretty much be because he has taken so long to come to terms with anyone. If he has thrown his last pitch in MLB there is a serious problem with his demands or MLB free agency.
Not saying he fits with the Sox but just because a few others has compared him to Shields besides you doesn't make it accurate.
This from Brooks baseball:
Basic description of 2018 pitches compared to other LHP:
His sinker is a real worm killer that generates an extreme number of groundballs compared to other pitchers' sinkers, has surprisingly little armside run and has some natural sinking action. His slider sweeps across the zone, has exceptional depth and has below average velo. His cutter has extreme cut action and has some natural sink. His change has slightly below average velo and has some natural sink to it. His fourseam fastball is straight as an arrow, generates a very high amount of groundballs compared to other pitchers' fourseamers, has some natural sinking action and has essentially average velo.
The thing that separate him is his sinker and the natural sinking action on his other pitches.