The law of less returns was kind of wobbly for the classic Trek films, as I recall. In terms of raw numbers, I believe TVH long held the record for most profitable Trek film of all time. I don't think it was dethroned until the Ambramsverse films came out, in fact. Now I believe if adjusted for inflation, TMP would hold the record for most successful of the original 10 films. But even then, TVH was definitely more profitable than, say, TSFS. And then TUC was clearly more profitable than TFF. So Trek was kind of all over the place.
Agreed. III did continue a slight downward trend, but everything official (interviews, etc) was that the makers wanted to switch to a lighthearted tone after II and II being so serious. A fair assertion for sure as both could be heavy, II more so. Like or dislike or anything in between, IV was lightning in a bottle, with later attempts to replicate it flopping more than that jumping salmon or striped mullet fish that miscalculated and landed on a dock until re-reaching the water again. Now imagine if the USS
Grissom was the same ship design as Enterprise... And even more fun, imagine
Excelsior looking like
Enterprise as well. In all honesty, it really would look cheap to reuse the same exterior - especially as nothing can be redressed to make it "within a template yet uniquely identifiable". The bridge set is an easy change (see
Reliant) and, noting
Excelsior's limited bridge set that looks more like a long line than anything oblong, with tacky green-glowing chairs. Hope that's not radium-226 or, worse, kryptonite as you know Kal-El could have a long enough lifespan then sign up into the Federation out of abject boredom, how's that for a crossover?
TTF was definitely breaking the mold in a bigger way - An audience member in 1989, I don't think many if any (I hadn't, for decades) had paralleled the tone of the film to the 60s show, because we were all expecting more of the 80s tone. That did it in the most, along with the misguided over-the-top comedy. Pare down as much overdone comedy and throw in the deleted scenes, the movie could be salvageable. It still does capture the human condition despite the foibles.
It's always great when the trend gets bucked more than the horses in that movie "Blazing Saddles", or at least thew cowboys eating beans next to them. TUC, while still having some of the ha-ha huff, did return to basics, managing to create an adversary worthy of Khan but without needing a previous TV episode in which to directly create General Chang out of - by taking undercurrents of the Klingon elements of III and IV and creating Chang from that. It was a refreshing rewatch when I saw it the other day. Some dialogue at the start is a bit clunky, but as the movie gets on it only gets stronger - and also melds the tone of the TV show with the 80s films as it was to be a swansong. (Didn't know that was Nimoy's actual art piece either, and Kim Cattrall not being available for the original Saavik, plus her research that led to "Valeris", right down to hairdo, was pretty cool. Also note that Excelsior ditched the half-baked bridge design and did a partial redress of
Enterprise's but to much better effect...