As a first time acting job, I thought he held his own, at least as good a performance as Kim Darby's...and a lot better than much of whats considered "talented" by today's standards.
I happened to be in the same place at the same time as my two brothers earlier this month, due to the funeral of a family member. It's rare we're together.
Post-funeral, one of the women in the home mentioned a movie and how bad an acting job someone had done in it.
We three brothers immediately looked at each other and, in unison, said "I ain't dead yet, you bushwhacker." Then we each shuddered.
You see, that was one of Glen Campbell's lines in True Grit, which we saw together as young teenagers.
Campbell's acting was so bad that it burned an indelible space in our brains. The Pavlovian response to the words "bad acting" was for the three of us to spontaneously quote Glen Campbell from True Grit.
To use the current vernacular "I'm just saying" he must have been pretty bad for three of us to remember it for that long.
Although he and Kim Darby (and Joe Namath) later starred in "Norwood." I'd say his acting was worse in Norwood, except that it didn't rise to the level of acting.