I don't mind device mapper, for what I used it for, multipath scsi.

mdadm doesn't need lvm. But if you want snapshots, or to have flexible partitions (anything like the flexibility of zfs) you need lvm.

Also for the longest time redhat used to force lvm on you by default. I assume this was to help with "flexibility"

In practice, on virtual machines, or anything back with decent storage, I'd remove the partition table and just run on the block device directly.