As people are saying, the clear and obvious objection to Monday morning quarterbacking the Taillon deal is that Contreras is probably just as good as any prospect who traded hands at the deadline -- Gray is probably better, and I suppose Madrigal if you want to count him or compare them.
But even setting that aside, I don't think there's a nitpick with process, which is more important than results still TBD for at least 1-2 years. Best case scenario looks like Taillon probably throws up 2-4 solid starts in July, increasing his value somewhat. Earlier, weaker starts are probably looked at more harshly on a bad team in a pitcher's park than a Yankees team in a bandbox, and there will always be the leverage of 2nd TJS working against him. You are not getting a Berrios-style return. Maybe you get something like the Cubs managed to get for Rizzo, although again, wildly different players to compare.
I do think given how he performed last year and what the market looked like this year, there's room to question the process with Musgrove (here the results much less, given that the centerpiece is barely 20). Musgrove had his question marks, but he looked to be fully turning a corner, and you probably do get a similar return as Berrios. He doesn't have quite the same pedigree, but he as a WS ring. His numbers have gotten slightly worse month by month, such that I think he really is just a very good #3, but he's enough to both give you innings and impact a playoff game.
That trade was a calculated risk -- Musgrove regresses and you probably get very little, or hold until the offseason and it's still a mess. The risk is now spread over 5 players who all are showing some good signs. Given where things stand, I think you could raise at least two specific, process-based criticisms: 1) higher upside, quality more than quantity return at the deadline this year; 2) extension candidate as a veteran pitcher to go along with Reynolds and Hayes heading into next year and beyond.
Either of those two options might be a better decision than the one that was made, but it's really an apples to oranges comparison, especially since the trade pieces are so spread out. Cruz might be an efficient mid/backend lefty, Head remains young and projectible, hitting for power in an environment where that is not common, Rodriguez continues to fly under the radar but shows promise, Bednar is MLB quality relief and might be leverage, and Fellows remains a dev project. You could realistically end up with three contributors out of that mix, and if one is a power/speed everyday OF, you'll be pretty hard pressed to think that even option #1 from above would have netted you a better situation.
Overall, my take on Cherington is that it's excessive to totally fawn over everything he's done. He's executed the first and easier part of a rebuild very well, by all signs so far, and now the big question is what's next. 2022 is going to be a real uphill battle after 100+ losses, but short of something stunning prior to 2023 (like signing a star), biding our time and sitting on our hands next year shouldn't be an option. San Francisco and Washington both showed that you can get above average veteran talent if you make smart decisions and are willing to pay for veterans on shorter deals. At this point we know who in the current organization is not an option, and have some new blood to look at as we wait for AA prospects to develop, which is likely a full year in most cases at least.
The next step for 2022 should be modestly investing in a few more veterans: pay a veteran SP 8-12M for a year and not just 1.5M on a lark. If nothing else, those kinds of moves for 2022 will give you some realistic and viable trade chips for next deadline -- being totally stagnant will have you looking more like a team like the Rockies, which is not a good thing.