No it's mostly sculpt. Stickers don't make the toy.

MMPR Megazord/Daizyuzin might not have the most complex transformation out there, but its components still require some effort to change and the set seems to avoid the kibble problem I mentioned early. Most of the loose components don't have parts sticking out that betray what they will become, which I think is a nice feat of engineering. Its only weak point is the pteranodon/pterodactyl, which is not that great on its own.

Compare this to Gokaioh, where GokaiJet has a very visible hand hanging below the cockpit, making him an arm with wings. GokaiRacer has a visible fist functioning as engine and GokaiGalleon has two legs sticking out of its back. Its combination basically consists of sticking all parts together with only minimal transformation of the individual vehicles.

This is why I feel Sentai toys are getting simpler.

I think Kyoryuger is still a complex toyline compared to some of the others. Just look at any review of Plezuon. It doesn't seem to be the simplest of mecha. Especially the amount of parts involved in its combination with Gabutyra. I would like to post a Youtube link to the Baltmatrix review of it, but then this post would be dominated by a huge embedded Youtube Video.

The focus on gimmicks seems to be a logical explanation. The aforementioned GokaiOh is a toy that relies on the 'greater power' gimmick to make him stand out, where it is able to automatically transform using parts concealed within its body. This unfortunately sacrifices the individual machines and combination sequence. The only gimmick older toys had was the transformation itself, making that the primary focus in the design.

I think your production cost statement also makes sense, as more modern Sentai lines have much more releases compared to the older ones. For example: Timeranger had 4 DX mecha releases, compared to ToQger, which had 9 mecha releases (2 of which, the Drill and Shield Ressha, were included in roleplay weapons).
It seems nowadays that Bandai puts all the resources, like time and money, previously used for 3-4 releases into 7-9 releases a year, resulting in simpler designed toys.

Yet it's still more complex than like the last nine years of mecha. And it's like 30 years old.

Mammoth is at least. Daizyujin's legs are the same in principal as GekiTouja.

Daizyujin isn't the most complicated mecha out there, but it's all about retrospective at this point.

To be fair, it does just involve sticking the legs onto the T-Rex and using the pterodactyl as a chestplate. The mammoth is pretty good though. But then we look at the Ninja Megazord, at it is pretty similar to today's. The only exception, again, is probably the torso.