tl;dr: The most critical "machine" in GT is the EBF, but the next-most important is the Vacuum Freezer. In order to make a Vacuum Freezer you need HV, so it is a waste of materials to build a complete line of LV and MV machines. The goal should be to make as few of those tier machines as possible, and go straight to HV as quickly as possible.
I concur in part and dissent in part. The LV machines are very energy efficient. From an energy efficiency standpoint, a full suite of LV machines and even multiples in some cases are best. But MV, yes, it is not worth it to build a full suite, just what you need. If you care about energy efficiency, MV electrolyzer and centrifuge are good for those recipes requiring those voltages. HV gets you the good macerator, so you probably do need nearly a full suite there. And thinking about it more, I think you almost have to build all of the LV machines to progress at all. But MV does have a lot of stuff you can skip.