Maybe it is, I don't know.

I was talking about your scenario of space-faring silicon-based life. If Venus can support this different life, then it should be already there.

It's hard enough to find signs of life similar to ours (something familiar, carbon, metabolism), so if there is some completely different life somewhere in the solar system, it's unlikely we would be able to recognize it at first glance. So unlikely, that is almost pointless to postulate its existence.

Therefore, our best shot is to look for life similar to ours (because we know its tells). I think that's where the idea of a habitability zone comes from. It's not excluding the possibility of life existing outside of the zone, it's just making it easier for us to look (because looking everywhere means considering things we can't possibly understand).

That idea has been slightly changed since we started to hypothesize life on moons like Europa and Enceladus though. They are outside the classical habitable zone, but they have other possible means for producing liquid water that don't rely on the heat of a close star (tidal friction and residual core heat).