And even if you discount Yoda's little outfit, look at what Anakin is wearing in the final scene of ROTJ.
Yoda's outfit isn't remotely distinctive or "Jedi"-like. He's just wearing a tattered burlap coat. Sure, the colors are vaguely reminiscent of what we think of as the Jedi look, but whether it was intentional or not doesn't really matter, since it doesn't truly connect visually to Obi Wan's outfit to form a consistent look. At the time of ESB, those were the only two Jedi we'd ever seen, so it's a stretch to say they were really "dressed alike."
I'll totally agree on the Anakin ROTJ thing, though.
But all that comes AFTER ANH. Clearly, in ANH, it was just a "desert" look. Later, Lucas changed his mind (ROTJ, maybe ESB, DEFINITELY the PT.)
Lucas is notorious for changing his mind, as we all know. But the original intent of Obi Wan's look was not "Hey, this is a standard, identifiable Jedi uniform."
Everyone always jokes about why Luke is "hidden" on Tatooine with his real name and how Obi Wan also uses his real last name, too, despite also being in "hiding."
Would be all kinds of extra stupid if he wore distinctive, signature Jedi garb while trying to lay low.