It is also possible that several of those designs were transition designs between the Ambassador style and the Galaxy style and thus fewer were built before the Galaxy-class started coming out of the yards. Or Starfleet found it easier to refit older ships like say the Excelsior-class USS Fearless rather than build as many midsized starships. Freeing up yards for the larger and more intensive Galaxy-class ships. They did have an engineer going around tweaking older starship engines early in the Enterprise-D's career.
There are 18 conjectural Starfleet classes from the ST Encyclopedia. At least 5 of them are canon based on their class names being listed on Okudagrams (Apollo, Bradbury, Korolev, Merced and Renaissance.) The others are:
Andromeda NCC-6XXXX-7XXXX (only two known ships of this class)
Antares NCC-1XXXX (only one known ship of this class)
Chimera NCC-5XXXX (only one known ship of this class)
Deneva NCC-6XXX (only one or two known ships of this class)
Hokule'a NCC-1XXXX (only one known ship of this class)
Istanbul NCC-3XXXX-4XXXX (only three known ships of this class)
Mediterranean NCC-4XXXX (only two known ships of this class)
Rigel NCC-6XXXX (only two known ships of this class)
Sequioa NCC-7XXXX (only one known ship of this class)
Surak NCC-3XXXX (only one known ship of this class)
Wambundu NCC-2XXXX (only two known ships of this class)
Yorkshire NCC-5XXXX (only one known ship of this class)
Zodiac NCC-6XXXX (only one known ship of this class)
And of the 5 above ships:
Apollo NCC-1XXXX (only four known ships of this class)
Bradbury NX-7XXXX (only one known ship of this class)
Korolev NCC-5XXXX (only one known ship of this class)
Merced NCC-3XXXX (only one known ship of this class)
Renaissance NCC-4XXXX (only four known ships of this class)
Then we have the BoBW ships:
Challenger NCC-5XXXX (only three known ships of this class)
Cheyenne NCC-7XXXX (only one known ship of this class)
Freedom NCC-6XXXX (only two known ships of this class)
New Orleans NCC-5XXXX (only four known ships of this class)
Niagara NCC-5XXXX (only two known ships of this class)
Springfield NCC-5XXXX (only one known ship of this class)
So when we extrapolate this info based on what we saw in DS9 and VOY, it appears that while Starfleet had lots of ship classes, almost none of them seem to have been built in large numbers. The only ones we saw in large numbers were Excelsiors, Mirandas, Akiras, Steamrunners and Sabers. We also saw Galaxies, Nebulas and Defiants in the fleet, but again only in small numbers.
Conclusion: It appears as though the Excelsior and Miranda classes were the primary two vessels being heavily constructed between the 2280's and the 2340's (with other classes with registry numbers between 1XXXX and 4XXXX being produced in much smaller numbers, and possibly resembling the Excelsior and Miranda classes), and then around the 2350's-'60's production changed to the Akira, Saber and Steamrunner classes being heavily constructed with other classes from the Galaxy family being produced in smaller numbers.
And, of course, none of this takes into account the Ambassador class.