Well Kyle Shanahan was inexperienced at one time too.
Young offensive HCs like Kyle Shanahan, Sean McVay, Matt LaFleur, Zac Taylor and even Mike McDaniel can all work but there tends to be a pattern:
(1) There is quality QB play.
LA: Goff & Stafford
SF: Garoppolo & Purdy
CIN: Burrow
GB: Rodgers & Love
MIA: Tagovailoa
Miami has done enough in this area to look elsewhere in explaining it's shortcomings. Tua might be physically limited but those limitations don't explain the Dolphins limitations.
(2) The teams hits on unexpected stars outside just R1.
Looking at just the 49ers, check out what gems they've found deep in the draft since hiring Lynch & Shanahan in 2017:
R2 - WR - Deebo Samuel
R3 - LB - Fred Warner
R5 - LB - Dre Greenlaw
R5 - TE - George Kittle
R7 - QB - Brock Purdy
It's major hits like that which took Seattle to the top 10 years ago.
Miami hasn't done enough outside R1. Hunt and Holland are solid R2 picks. They're starters, but not nationally-recognized star pieces. Hunt is great but he's a Guard. Achane in R3 may qualify in time. There are just too many non-contributors from the '20, '21, '22 and '23 drafts if we're being honest.
Complete no-shows like Noah Igbinoghene, Hunter Long, Erik Ezukama, Channing Tindall and Cam Smith have pretty much been the norm. We're reaching to call guys like Raekwon Davis a hit when he's eminently replaceable. Austin Jackson turning in a good season is a "thank God" moment.
(3) A strong defensive unit with deep talent is present.
Miami's done a good job building this unit filling gaps in any way they can with FAs, UDFAs, trades, draft picks and re-signings. Bringing in Vic Fangio is good but it's going to take picks & $$$ to ensure that unit plays well going forward. Part of that is the lack of Channing Tindall, Noah Igbinoghene, Cam Smith, etc. It's also someone like R2 pick Raekwon Davis not being a more integral piece and basically having lost his place to a now more important Zach Seiler. It's R3 picks like Brandon Jones and Channing Tindall doing very little for you and having to be replaced by outside FAs like Deshon Elliott and David Long Jr.
Take-away:
If it feels like Miami is a step behind consider that maybe it's because they really haven't had a home-run draft that would gain them sufficient ground and stop them having to chase quick-fixes in FA.
At some point, Chris Grier is going to have to "win big" with the draft. While we can point to some solid picks, we simply haven't gained enough value there to be in a better position hence we're choosing between competing objectives at the same time:
(A) re-sign the QB
(B) rebuild the OL
(C) keep expensive players hitting FA: Wilkins, Van Ginkel, Hunt, Lamb, etc.
(D) retool the defense so the Vic Fangio acquisition leads to something
Mistakes have been made. We wasted years 1 & 2 of Tua's cheap rookie deal hiring the wrong HC. The OL rebuild was botched with bad picks and some losses to FA. Lots of picks & money were spent on a sexy WR when maybe that wasn't the most prudent thing for a still-rebuilding team.
At some point, Miami just has to do better on this team-building thing. It's hitting on players, having those players stay healthy and profiting from their performance relative to their cost. The obvious place to get that is the draft, where players are young and cheap.
This is why I think letting go of Tyreek (if anyone would take him) would also help assure you can keep guys like Wilkins/Hunt who would probably add more long-term value compared to another couple years of Hill producing wild stats--or worse, collecting $30M all while the coaches apply a governor to his catch/yards totals to make sure he's not overused. Sorry, but it's hard to imagine feeling good about paying $30M for 1,200-yds. Tyreek
better produce 2,000-yds if he's being paid $30M and yet that kind of offense is one we've seen fail.