Well, its not a sin, first of all. Second, you listed two players who are the idols of many bass players around the world who took, or still take, many solos. The bass can solo, and there is nothing wrong with it at all. I saw Stu Hamm play a solo at a Satriani concert that blew my mind because it was still melodic, even with all the technical playing he was doing.
But, soloing on the bass isn't for everyone and there is nothing wrong with either approach. In my particular case, I have been in bands where I was encouraged to take a solo and I shied away from it. I got plenty of recognition at gigs for my playing without ever taking a solo and I never felt like it would have suited the music we were playing.
I also play bass in a prog-metal band where the guitar player wrote a song with a lengthy bass-solo section, doing so with me in his mind. I was not comfortable with it, but since he thought enough of me to do this without my ever seeking that kind of limelight, I took it as a very big compliment and tried my best to do a competent solo. And I think the results were pretty good, I don't cringe too much when hearing it now.

But, I would rather try to make a statement with my rhythm playing because I think that is what people will remember more. When you look at a guy like Geddy, he takes very infrequent and brief solos, but his bass lines can be very technical and demanding, yet still have an essence of groove and/or melody. That is the approach I prefer.
That said, my approach may not be the same as yours and that doesn't make either one of us wrong. If you feel the need to solo, and you have something worth saying on the instrument, you should find a way to work some soloes in. My only advice would be too not neglect the rhythm for the sake of a good solo.