First off I'll be the first to admit that prediction is an inexact and oftentimes fruitless art. If it has any utility outside of placing wagers, it is in the setting of expectations.
In terms of the players lost versus their replacements and believing practice reports, my experience is practice reports are grain of salt types of things. High ceilings are real and can be good guide, but it's difficult to predict when a player is ready to maximize. There have many players drafted as upperclassman that played as freshman and sophomores while being real liabilities on the field.
IMO.. Brooks never looked amazing, which I'd call an elite college FB player. I would say he flashed upper tier ability at times and looked stickier in coverage than Jamison. It does appear that Texas has 4 corners who can give starter level reps, which should be a boost to the secondary. Catalon also offers the potential for a big upgrade at safety, pending health and whatnot.
The Edge position's most concerning element is the weakside. Ovie was horrific at pass rush, but turned into a reasonable edge setter. That's the biggest concern with Burke or whoever plays that position. Replacing DMO with Gbenda is also a potentially big drop off, even with DMO not playing great tactically at times.
Agreed on WR and TE, nothing really to fret about there.
Assuming the oline becomes good with one more year of development is a big stretch imo. Connor and Majors were two of the worse run blockers in the conference last year. Is it possible they improve, sure. Should we expect it, imo not sure. Even if they improve, how much? Is Campbell at RG the upgrade we expect as a true sophomore? The unit overall was pretty good at pass blocking, which is Majors strength at center. The tackles make this a bit easier to manage. Biggest area of concern is run blocking, which many have hit on here.
Good bet Ewer's improves, especially given the targets he has and an elite left tackle. Does he become a good college QB or elite? Based on what I saw last season, I believe good is more likely.
IMO... the rosy outlook of we've improved every area is a little too rosy. This team should have a really good passing offense, but will the running game be good enough for the offense to function against good defenses? The passing defense might improve, but can Texas actually sack the qb and produce turnovers? Can they get off the field on 3rd and 4th down? Will the run defense hold up, with the weakside edge being potentially weaker? The point is this team has unknowns, so do all the other teams in the conference. They don't have enough knowns for me to feel as confident as most of the fanbase appears to feel.