But they dont have anyone thats strong enough to be the leader.

Because their leaser is still sealed away. Which for Sentai is also nothing new or groundbreaking.

How would be a boukenger-like sentai ?

1) Why Goseiger's mecha didn't go so well?

2) What would it take to make Goseiger better?

Nothing, to answer your second question first. Tensou Sentai Goseiger was episode after episode of absolute perfectly. Character, story, and quality. Buredoran is the absolute best Sentai villain in history (Candelira is no longer villain, making her the best female hero ever). And Alata is one of the most underrated Red Sentai in the history of the franchise.

And the Mecha were Zord Builder before Zord Builder. You can do anything with them. Connect Headders wherever there's an open port, and there are a lot of open ports.

In closing, Watch Goseiger. Everyone watch Goseiger.

Have tried to re-watch. Isn't a bad series, though at times I feel that Buredoran's build-up is more enticing than any actual character reveals. The Goseiger themselves have a tendency to say the same thing over and over and new "Mecha" pop-up before the most recent set can do much. On top of that, I will say what everyone is thinking, Saban and co. could have easily done Megaforce 10x better than it turned out.

Gosei red looks like justin bieber.

.. Someone hold my necklace.

Dude, aside from the bowl cut, I do not see how you see that. Alata looks nothing like that.... You know what? Just hope-

Too late. Sentai, be gentle with the kid. Not everyone knows how to handle your rage.

I think you should watch Goseiger. Alata is a cinnamon roll who would die to protect you (Thank you Pocky and Cranky on Twitter for that). He is nothing like that person, for one thing Alata has a soul. I understand they might have similar haircuts, but they are absolutely nothing alike.