> history is basically unusable.

I can see how, in the second workflow (feature branch workflow), this can become a problem. If the history looks like this

        ---------
       /         \
    --A           E--
       \         /
        B---C---D

then we can sort of guess that commit B started a feature branch and E is the merge commit that merged the feature back to master. And commits B, C and D can be "unusable" intermediate work, maybe even uncompilable. But if nobody ever works directly on master, all development is done in the feature branches, then when E has two parents, A and D, and A is a merge commit and D is not, then you know that A is in the master branch and D was in a finished feature branch.

This gets more complicated in the third (gitflow) workflow, when all feature branches also have their own "feature master" branch and developer branches. Then all commits in the several "feature master" braches are merge commits, and then all the commits in the main master are merges from those merge commits. Then a commit in the master branch has only merge commits as its parents, so how can you tell which one of the parents is the previous commit in the master, and which one in a closed, finished feature branch?

If you could tell, then when bisecting or whatever, you could first just go back in history in the master, and only when needed, take a look at more details in the feature branch commits which contributed to the single merge commit in the master.

All this is solved by the named branches in Mercurial, where a commit carries forever a nametag, to which branch in originally belonged. You can add informal extra info in git commits in commit messages, so with some extra tooling you could make the history in these branching models usable again.

Then again, in the fourth workflow (forking workflow) when developers pull directly from each other, and there is no central repo, permanently tagging a commit with a branch name would make no sense. And this is the use case with Linux kernel work, for which git was originally designed.