I mean, TMP, which literally DOES have a TOS episode plot for its premise, is one of the few Trek films that almost never gets the "TV episode feel to it" criticism, so that particular knock strikes me as arbitrary, a way of saying you didn't like it without really explaining why.
I don't think I've ever seen a review (well, at least not one written by someone familiar with the series, be it the SF press or fans) that doesn't point out it's got virtually the same plot as The Changeling
. Isn't "Where Nomad Has Gone Before" one of the derogatory fan nicknames for it? Though TMP does have in its corner to counteract that some really top notch state of the then art effects to add a cinimatic gloss to it that stops it even slightly feeling like an episode of TOS. It's still as dull as dishwater though, so avoiding the small screen feeling doesn't help so much there.
As for more mainstream critics not making great play of the TNG films feeling like TV episodes, that's likely down to them generally being a lot less familiar with what the shows like the fans are. If they were being harsh they'd sum up the events of Insurrection
as inconsequential compared to the other films rather than "Like a filler episode of the show".