[tauoverpi]

You don't need everything to be generic to have safety as the API provided by the object using the linked list can maintain safety by making it difficult to do the wrong thing and being correct by construction. Of course that doesn't stop a user of a library ignoring the safe way to handle types which use intrusive linked list nodes but that same user is likely going to shoot themselves in the foot regardless even when given a "safer" interface.

Trying to write a safer version of the above without losing the performance / advantages takes you into the realm of ATS2 https://www.cs.bu.edu/~hwxi/atslangweb/ which quickly becomes more difficult to work with than practical (and no, rust can't solve this with it's implementation of resource types as far as I'm aware).

So yes, doing the above makes sense when the problem demands it as allocating memory you don't need when there's a clear way to represent a graph without it just wastes cycles on memory management you didn't even need to do.