That is an ongoing problem with the show. I had to force myself to ignore that question every time it reared its ugly head.

Well said, sir.

the mechs were essentially transformers that could combine, what isn't marketable exactly?

THEN you have to wrap your head around the idea that magic, giant robotic animals and spiritual kung fu all rub shoulder to shoulder in the same universe despite each one defying one another, and the very laws of nature itself.

Well, they can still tell a good story and be intelligent. As much as saying they're 'dark intellectual thrillers' is over-hyping them, saying 'oh they're just toy commercials for three year olds' are selling it a little short. I mean most Rider shows would at least be rated Y7 over here, haha.

Which is exactly why I'd prefer all of these stories take place in separate universes. And why trying to have installed a sense of ongoing continuity may have been impossible.

But for Gokaiger, because in my head it takes place in this weird Versus universe where everything is a bit askew, I find the weird incongruities appealing. Makes my brain work hard to figure out explanations. (I believe that is known as a fanwank. :lol)

They don't have their powers in Gokaiger. That's a major thing in the show. The Legend War at the beginning left every single past Sentai powerless, and those powers now reside only in the Ranger keys. The past Rangers could maybe help the Gokaigers fight off a few mooks, but otherwise they can't offer much more help than unlocking the full power of they keys.

The Gokaigers could repower all the teams by giving they keys back, but that would mean giving up the greatest treasure in the universe.

Characters like GekiRed, who fights with mystic martial arts or characters like MagiRed who fights with fire magic, there is no excuse for them to not be helping. Ranger costumes or not.

They don't have their powers anymore, though. Kai specifically said he had lost his magic and later Ryo can't use Qi-Power anymore either.

As for the mecha, this is actually apparently explained in the 199 Heroes companion book. Apparently most of the mecha were destroyed by the Zangyack during the Legend War, although in the movie proper we only see a destroyed Gosei Great. Apparently the book also explains how the dead Rangers were alive for the War, but I can't find it translated anywhere.

But at the end of the episode with Kai, that fire spirit thing appears which explains how he created that fire trap. It doesn't explain why they aren't fighting, though.