And hell, even an "execution safe" configuration can contain malware if there's a parser bug.
At some point you have to choose who to trust and not to trust to write code that runs on your system, and all you can really do is try to verify that they did in fact write it, and run untrusted code in isolation from sensitive data.
There are way more configs out there than there are software projects.
I think the real problem is around being able to trust your entire system. It'd help much more to have a better capability system so my rouge text editor can't upload my photos or credit card info from my browser profile to the internet, but today things kind of work because of tons of well intended and behaved people collaborating.
[0] https://index.scheme.org/filterset/r7rs_small/%28scheme%2520...
[1] https://index.scheme.org/filterset/r7rs_small/%28scheme%2520...
[2] https://index.scheme.org/filterset/r7rs_small/%28scheme%2520...