Agree on most of that, but by an upgrade I meant the ability to actually play and contribute. Hollister had one great catch against the Jaguars, next thing you know he was hobbling around and favoring his leg. And he hasnt been playing much (or at all) since then. Allen is a fairly good blocker but when the passing play is set to unfold, he acts like a guy who happens to be on the field for no apparent reason. Patriots had great two-pronged TE punch with Bennett, even with Tim Wright, nowadays it is nearly impossible to replicate that with oft-injured Hollister or statue like Allen.
Wright was pretty much blocking averse. He wasn't even as willing to block as a Pats' WR. That's why he only lasted the one season in NE. It may be one of the reasons that he's still looking for work in the NFL since being cut this season by both the Lions and the Chiefs.
You have the sequence incorrect wrt Hollister's injuries. He was out wk-1 with a hammy, then played through it in wk-2 v. the Jags. He was off the injury report completely for the first two practices of wk-3 (no hammy issue), and then suffered a chest injury (highly unlikely to become chronic) that kept him out for wks-3 & 4. He played in wks 5 & 6 (mostly on ST), before re-injuring his hammy and being out wk-7 and, now, wk-8.
So, neither Hollister or Engram missed any time to injury as rookies, and both have now missed 3 games this season to leg injuries - Hollister/hamstring; Engram/knee.
Allen isn't merely "fairly good" as a blocker, he's probably among the top 3 or 4 in the league (as is Gronk). Martellus Bennett was also a top-10 blocker. And that "two-pronged attack" with Bennett and Gronk back in 2016 spanned only 6 games and about 350 snaps - from game #4 thru game #9 - when Gronk was healthy. The Pats
lost two of those six games, including being shut out by the Bills.
Hollister was a very willing blocker as a rookie, he was simply bad at it - about the same level as Engram. Engram was successful as a receiver in the Giants' system, but then, so was Will Tye. Tye was in the Pats system from mid-October
last season, through OTAs and Camp, and still didn't "get it". I wouldn't bet on Engram being able to pick up enough of it between now and the end of the season to make an impact. The odds are much better that Hollister will heal up and contribute something.
All of which is why I made the point of noting that Engram wasn't a lock to be an upgrade over Hollister unless Hollister was on IR.