I do agree that Flowers injury hurt us, but Flowers isn't an impact rush guy, IMO. He is good, don't get me wrong, but he isn't nowhere near elite (think Bosa Brothers). I don't think he is even a step below elite (think Shaq Barrett, Frank Clark). He falls into the next group with the Melvin Ingram's of the world. A borderline pro bowler, but not an All-Pro. Honestly Okwara's emergence offset whatever we lost from Flowers.
Nick Williams though was a terrible signing. He has been a rotational guy at best his entire career. He had a decent pass rushing year before he hit free agency, but we should not have expected him to be anything, but a nickel rusher. Shelton has never shown more then being a space eater and he was just average at that. Was pretty much the same thing for us when he played. Going into the season that D-Line just didn't have enough NFL talent. Bob Quinn either grossly over-estimated the talent we had on the D-Line, or grossly over-estimated Patricia's coaching ability.
Flowers is a consistent pass rusher. We would have had 3 if Flowers stayed healthy with Okwara and Griffen. They never played together. Williams had a nice 2019 but Quinn didn't give him a huge contract. Maybe they expected to add one in the draft but then went Okudah route. And J Okwara injury killed any potential there. No Davis blitzing for some reasons or much blitzing at all but probably due to coverage issues by LBs and safeties. And not like FA is chocked full of stud pass rushing DTs anyway.
The pass rush could have been good enough or had potential to give us a better defense. Things/injuries derailed that or things weren't executed and schemes were bad for it.
Let's see what 2021 brings and who stays. Flowers, Hand and J Okwara for sure is a start. Now add more