You never heard of the rule that every second Trek movie is good?.
Its not a rule.
Star Trek: The Motion Picture "earned" that distinction by being creatively buried by TWOK saving the then-fledgling ST film series by restoring what is perceived as the natural progression from the tone, characterization and cretive strengths of TOS. TWOK's follow-up--
The Search for Spock--did not fail commercially or creatively; it was a dramatic showcase for several characters, had many of the franchise's most memorable and heartfelt storylines / elements (Kirk's love for his friends / seeing the power of faith through Spock's revival with his Katra / Kirk's tragically short-lived relationship with his son / the mind meld sequence / destruction of the 1701, etc.). It was the logical conclusion to threads left by TWOK, continuing the TOS feel in the movie era.
Where
The Final Frontier is concerned, I will always say its not a bad film at all. Shatner knew how to direct a
Star Trek film, and with its focus on the bond between the Big Three (and exploring their personal pain), TFF gave ST fans some of the best character development seen in the movies. One really understood just how bonded the Big Three were to each other, no matter the misery they've suffered. In fact, the personal pain Spock and McCoy endured in earlier years explains the how and why their connection (despite the head-butting) or need to make a new "family" bond had occurred throughout TOS (and in TWOK / TSFS); they have blood relations, but only
they truly understood each other.
That said, there are certain fans with personal agendas which fueled their ranting against the film, which are not supportable positions, such as
"S-Shatner b-b-brought religion into Star Trek!!!!" as if
TOS had presented an atheistic universe. If anyone ever
watched TOS--a production when Roddenberry actually had the most control during his years associated with the franchise--they would see religion and faith existed in-universe, with characters expressing belief, quoted Biblical scripture and with Kirk, he had a habit of breaking
false gods (see: Gary Mitchell and Apollo), letting them know they were not the real deal. This was the work and views of the various creatives, not some nonexistent mandate from NBC, TOS' sponsors, or any other organization.
Some dislike TSFS for many of the same reasons, as they despised the entire creation and use of Vulcan spirituality / practices and the fact Spock's Katra was not the equivalent of a program or transporter pattern, but his soul by another name, and the only way he could return to the physical world. Without it, that body was simply an unconscious slab of meat. Over the decades, i've witnessed the fits of rage about this sub-topic (especially into the Berman era), and despite ST--as a franchise--establishing faith and religion among its in-universe history, some target movie entries 3 and 5--the so-named odd-numbered entries as "bad", usually for that reason.
Regarding the TNG movies...well, there's a Star Trek-emblazoned trash can where they will always have a permanent home.