I find this complaint against IX is similar to the "Linear Design" of FFX complaint, where it was an actual complaint against the game on release, but as time passes and newer generations come, the issue has just become more obvious with age.

For IX, it is slower than it's predecessors. Partly because of the long intro animations for every battle, partly because the ATB gauge is criminally slow compared to the last four entries even with the Battle Speed set to it's highest standards. This is actually intentional because the game is suppose to invoke a feeling of the NES entries Regular Turn Based combat since the game is suppose to be a nostalgia title.

As for what Fynn is mentioning with FFVII, he's basically talking about how the ATB Gauge will completely freeze whenever you use a summon, limit break, or major spells. These are usually accompanied with camera tricks and stuff and the point is the combat is pausing for the sake of cinematic drive. With that said, the ATB fills up noticeably faster in VII than say FFVI, and it does have some time saving features like a unique "group hitting" animation for the basic Elemental spells instead of the previous entries tendency to simply cast the same spell for every enemy, shaving off a few seconds here and there.

In truth, I feel that FFXII is the fastest entry in the series, where even special techs and high level spells eclipse X-2's mechanics since both the ATB requirements feel more manageable and you don't have to deal with the Garment Grid nonsense for prep work. Gambits also help of course. It was not uncommon to have battles end before you even realize you were in one.