Leslie, I doubt that a bit. Yes, SELinux protects most system processes very well but it doesn't confine most applications.
For example, Firefox is
not confined by SELinux in Fedora (but
it is in Gentoo - so it's not a SELinux limitation but a design decision by the Fedora developers who are afraid this would break too much for many users). Hence, if malware is able to break out of Firefox it could probably not seriously harm your system (unless it could successfully gain root rights) but it could, e.g., delete/manipulate your data on your home partition. This also applies to most other user applications like LibreOffice, PDF viewers, image viewers, multimedia applications ... which aren't confined by SELinux, either.
So what I do and strongly suggest: Use
Firejail to sandbox those applications. It provides a strong
sandbox (based on namespaces and seccomp-bpf), is relatively easy to use and comes with ready-to-use
profiles for many applications which usually work out of the box.
After its installation I recommend to execute
sudo firecfg
which creates symlinks in /usr/local/bin for all applications for which profiles are available (
symlink invocation). The next time you start them they will be sandboxed by Firejail. You can also create new profiles or modify existing ones in ~/.config/firejail which take precedence over the ones in /etc/firejail.
I hasten to add that I don't think that Linux desktop users are particularly endangered species. Nevertheless, recent examples
demonstrate that the Linux desktop is not as secure as it should/could be. Firejail is an easy and effective way to improve that situation.