Their FF output in the 90s was much higher than now.
The premise isn't exactly true either. Cursory look at the listings of games via Wikipedia:
Games with FF in the title 1990-2000: approx. 20
Games with FF in the title 2001-2010: approx. 44 + 6 mobile titles
Games with FF in the titel 2011-2016: approx. 15 + 39 mobile titles
Certainly more experiments recently on mobile, bolstered by many mobile rereleases. The shift to having less console or numbered titles releasing (including direct sequels) for the first time is less:
Numbered FF first releases in 1990-2000: 7
Numbered FF first releases in 2001-2010: 6
Numbered FF first releases in 2011-2016: 5
The 90s benefited from a couple of SNES and an NES release. The 2000s played fairly comparable. The 2010s dipped into more direct numbered sequels than before, but certainly befitting the AAA quality level inherent in the numbered series, and that's ignoring AAA games that weren't given a numbered entry.
But that goes back to my earlier point. Output for the series is gargantuan, appealing to tons of different games styles, platforms, remixes, remasters, sequels, episodic, expansions, experiments etc. It's such a massive offering that there really is something for almost everyone. Granted there isn't a general consistency in all that's there.
They had a formula that worked, and they produced three very successful games with lasting appeal.
But I kinda feel like the output across the 90s was widely different, and jumped a couple platforms (NES/SNES to PlayStation, 2D to 3D, TB to ATB, Pure-fantasy to SciFi, Cartoonish to Realistic and back).
Because ultimately I don't think most FF fans care about them being bold with each entry, etc.
Personally I do want this, but that's me and anecdotal.
Like, XIII wouldn't have been such a huge blow to the series if they'd had the next SP entry out two years later.
I think the consideration when planning XIII was that XIII-2 was the next SP entry.
Tabata, IMO is both right and wrong. It's possibly a disease to think that FF will succeed if only it is shaped by the crippling ideals of a few long-term thought processes, but likewise won't win simply by innovating either. There are very few things the series has guaranteed for a very long time--which is only easier to think when we think upon our favorite entries as not too long ago or say things like few games have come out between then and now.
Personally though, I would never want them to just 'stick to what they know'. I love the concept of this series, above most, as being the one to 'try something new'.