George couldn't make other colors due to technological limitations in the OT, so that wasn't a mistake.

The color of a saber is also deeply symbolic, and is why George chose the colors he did in the prequels. If he just used all of the colors it would have made the symbolism he was establishing far more ambiguous. I would argue that this is exactly what The Acolyte has done by deciding to include so many colors with no real character development behind the Jedi who wield them.

If you had done any research, you would've found out that a dual-sided lightsaber was used to employ a specific one of the lightsaber forms that Maul specialized in.

It wasn't a gimmick as you're suggesting, and the only reason Maul ends up using it as a single-sided blade eventually is because Obi-Wan destroys one of the halfs during the fight. Not to mention that a hilt as large as Maul's is a dead giveaway of it being a double-sided blade.

If he had tried the nonsense you're suggesting, he probably wouldn't have lasted 5 minutes due to not being able to use the lightsaber form he had trained extensively in