Because people disagree, doesn't mean that it's wrong. It a matter of opinion.
Froholdt is at starter level in the NFL IMO. Not pro-bowler. Not horrible. Still the 2nd highest ranked OL on the team per PFF.
In the grand scheme of things, how good is the second-highest-graded OL on a 1-6 team?
I like to think of it like this:
(1) where would he rank as the starter on a playoff team?
(2) where does he rank among the other starters at his position?
It is hard to evaluate OL play as a layman and from the outside. Extremely hard. That said, I think Froholdt could be the 5th best OL on a playoff team, and he's among the bottom third of starters at his position.
There are places we're much, much worse. Center is alongside TE for me a position that's difficult to scout and get value from with a high pick. There are other problems to focus on.
For example, the absolute zeroes who have been playing to Froholdt's immediate left.