Ex-Aid didn’t have two-parters, and Ghost only used them for a bit in the middle, and then a lot toward the end. Most of the Phase 1 period lacked them also, like Kuuga, Hibiki, or Kabuto.
Many series have had two-parters in them, without becoming reliant on them. Even Gaim did, once or twice. The only series that relied upon them, that I know, are Den-O, Decade, W, OOO, Fourze, Wizard, Drive, Zi-O, and arguably Kiva.

Zero-One could easily be like Ghost and start relying on them heavily later on, as it’s first real two-parter was the Ryouma arc in January.

I don't mind two parts; seems you can tell a slightly bigger story when you have 50 minutes instead of 25.

I thought 'W' did it best however, and it fit the 'two parts' theme of the show

That whole format really only started with Den-O in my mind and ended with Wizard. Drive had a bunch of two-parters early on but the format didn't last the whole show. The only really recent show that worked on that format was Zi-O, which was entirely two-part episodes, one four-parter in the middle and then eschewing arcs in the final stretch.

pretty sure it started with 'W', the entire season was nothing but two-parters.

I very distinctly remember Den-O, Kiva and Decade being almost all 2-parters as well. But I could have sworn that was the case with Hibiki and Kabuto too...

Den-O follows the 2-part format pretty strictly, and since it was Den-O levels of popularity, that set the part for the next few years (until Gaim, really).

It was. The older shows had more ongoing storylines, though, which made the two-parters feel less episodic than the monster/victim-of-the-fortnight we got from Den-O on.

The early episodes structure in Zero-One seems to remind me of Sentai, with how it has single episodic episodes.

They where also quite gory, Kuuga and Agito are a bit absurd in how much murder goes in per episode not to mention how nasty some of said murders are, Kuuga is kinda notorious in that regard but still.

But when I watched through all of Agito a few months back it was pretty much two episode plots, though quite often there where more then one of the "monster of the week " as well, so the Rider would be killing shit often enough instead of random flash of dust ESCAPE, though tbf that trope is still there and I do not mind it that much, a fun cliche anyways.

Overall the murdering kept happening up to Kabuto and then it kinda stopped, I can only really recall one episode in Den-O where the monster won and the victim got deleted anyways, though it has been a few years since I watched that so, but the two parter thing seems to have been a thing most of the time, they just seem to have cut down on meaningful plot in some season to a heavy degree.

Kiva and Decade still had monsters that killed, but Den-O set a lot of trends for the Neo Heisei era, including the less fatal monsters.

Quite a bit of fatalities in Zi-O actually when I think about it, and Build, but considering how both shows ended, they basically got a "makes it easy" in regards to dealing with the body counts.