thousands? i'll assume that's an exaggeration, since even a 20-year game would only be 1,040 turns (weeks).
Exaggeration or not, explain why it should be that good for only one point.
i'm pretty sure it's a lot less often than that. 25% would mean you complete a tech as a result of creativity every 1 in 4 turns,
No, it does not. It means that, over thousands and thousands of weeks, you eventually get an average number of successful creativity tech completions that, eventually, the percentage of time it works ends up to be about 25%.
You're thinking of how creativity works the wrong way. 25% chance of working doesn't mean I'm going to get a free tech every fourth turn any more than flipping a coin ten times means that I'll get exactly five heads and five tails every time.
Since you haven't run a test bed to see if it does, in fact, have a 25% chance of working each turn, I suppose we'll just have to take the tooltip at it's word and assume it does give a 25% chance every week of finishing your current tech.
but i really do not think it's over powered, and in fact, i'd tend to say that it's one of the less useful ways to spend your bonus points. i never pick creativity in a serious (MV) game, and only rarely research, and i don't seem to have any problem out-teching the AI on crippling and even maso most of the time, with or without tech trading. i think the ability picks are pretty well balanced for the most part, though a couple might be under-powered (trade/trade routes come to mind). but that of course is just my opinion.
I would suggest using it more often before you assert that it's fine. The inherent problem with creativity is that it is random; it is, at times, far too good for 1 point, and at others barely good enough. The best thing to do is find a way to alter it in such a way that it keeps its flavor while trying to lessen the randomness of it. Doing such a thing would make it far easier to address its value as far as points go.