Here's what I believe:
The draft is NOT a very good predictor of NFL success. It's not an objective measure of "talent". It represents the consensus on a very rough measure of potential, that, more often than not, becomes a popularity contest.
That said, in the context of all of the 31 other teams, a prospect drafted in the 1st round is certain to "make the team", and is almost certain to be installed as a starter in his rookie season, almost regardless of the flaws in his game - due to the ego of ownership and the job security fears of FO and coaching employees. He's also almost certain to receive the majority of the coaches attention - often at the expense of the development of later-round draftees and UDFAs - for pretty much the same reasons.
While many such high draftees do work out to be decent to high-end contributors (sooner or later), nearly as many don't. And many of those who do become multi-year "starters" end up being no better than, and often worse than, player drafted in the 3rd, 6th, or signed as as UDFA.
WRT the Pats, specifically, in spite of the fact that they rarely draft high in the first round (or any round, unless they've traded into that position), have had a somewhat greater success rate than most teams, mainly because they do all their own scouting (and even they still get it wrong - just not as often). IOW, if the Pats were to trade up in the first to take an LT, the odds are significantly high that the prospect will be successful - because it's the Pats.
However, the notion that it's somehow inherently worth it for the Pats to trade up for an LT prospect "because the odds of him making the team and becoming a starter" are in some not-quite-objective measure are "greater" --- nope.
The Pats will evaluate all the prospects as objectively as they can (while completely ignoring the media hype that gets fan engines revving), and then take the prospect who they think has the best potential to succeed at doing what they need him to do. And they'll take him when they need to based on how popular he is among the other 31 teams - no sooner, no later. If there's a lot of competition from other teams, they'll take him earlier. If there's not so much, they'll take him later.