In my mind, it's more like a library of scripts. Scripts are powerful and could potentially do anything, and it would be wise to not run these scripts arbitrarily without reviewing them first or having some other trust basis you can rely upon.

For example, I don't think you're expected to review all open source software on your system. It's much easier to instead trust a group of people with high visibility, such as the core Debian developers, and proceed to exercise graduated caution according to the likelihood that the code has been reviewed. You probably don't need to review the Linux kernel. When it comes to random widgets and themes off the internet, it's easy to encounter code that has never been reviewed.

I think there is such a thing as a risk tolerance. You can't build a completely trust-free computer. For practical and economic reasons, you're going to have to trust somebody. I think the optimal strategy is to be smart about who you're trusting and where you're focusing your limited resources to review. Popular Debian packages? Probably safe. Widget by person you've never heard of that nobody else uses? Probably risky.

If this makes you feel uncomfortable, I suggest that a person takes a few moments to review their threat model. What kinds of attacks are you worried about? What costs are you willing to pay to mitigate these attacks?