Too much time has passed.
Is this grammatically correct? Wouldn't it be better to say
Too much time has passed by.
Too much time has gone past.
The titular question is perfectly valid; "passed" can be used in relation to time without an object or preposition to mean "elapsed."
No, there is nothing wrong with "too much time has passed" because it is unambiguous and sounds natural.
In fact the second examples, whilst being technically correct, verge on sounding stilted and so because they are a step closer to unintelligibility are less "correct".