I have a fileless, execless copyfail exploit that works by injecting shellcode directly into systemd's pid 1. (I should probably publish it at some point...)
There's no reason the task should even be assumed to be executing code in a file. A process can map code into anonymous memory and continue executing there without even branching. Again this is considered a feature of the system rather than a flaw.
In a serious environment you'd run IPE with dm-verity/fs-verity to ensure binaries are whitelisted and integrity-checked at every execution.