Yeah, most distortion circuits boost the midrange frequencies, which effectively decreases the high and low ends, and that isn't exactly where you want to go with a bass. Most of the time.
The old style capacitors lose the most capacitance (ability to store voltage), some of them as much as 10% a year (!), which would effectively take them out of some old circuits. But carbon resistors fade too. A lot of the old components were made out of organic stuff that changes over time. Even potentiometers change, and their resistance values change. If that wasn't enough, capacitors and resistors are also affected by temperature. So those germanium transistors sound different when they are cold compared to when they are warm. It's a little crazy. When you buy an old Cry Baby or distortion box you never really know what you're going to get until you plug it in.
It's a little funny to see, say, guitar makers using the old style capacitors in their tone circuits. It isn't the capacitors themselves that people like in a vintage Gibson (for example), it's the aging of them. But the whole guitar ages - the wood dries, the nitrocellulose finish cracks (which sounds bad, but is really a good thing) - and you can't duplicate or fake the passage of time.
Okay, wake up everybody...