Hifi vs. Midfi vs. Lofi… categorical distinctions that are so subjective as to be more confusing than not; mostly marketing terms in how they’re used. Hifi stands for high fidelity - i.e. gear that will play back music with as little alteration to the mastering as possible - add no sound signature past the digital file, cassette, LP etc. Some nice kit by design is in a technical sense not great for the task of true hifi (again, by the literal meaning of the abbreviation). Much kit marketed as hifi is essentially unverified by real / legitimate testing. Hence hifi being more of a marketing moniker in the real world.
Midfi and lowfi came about as relative descriptors of kit that generally revolves around more widely affordable price points - you don’t tend to see folks talking about these three categories in terms of measurements or experiments with proper sampling, so the previous comments alluding to the terms being a way for market tier-ing and purchase-validating seem fairly accurate to me.
How hifi something is has nothing to do with how enjoyable it is to you. Some folks like a lot of “sound signature” from their kit be it from particular tubes, specific peculiarities of speaker cabinet or baffle design, etc. Believing in hifi is believing the mastering job of all music playback you consume needs zero further alteration in-playback chain (or in-room). Of course, many folks will agree that’s often not ideal.
Technically, how hifi a product is has absolutely zero to do with its cost. If something is expensive and has no available metrics / comparative studies to support its ability for (technically, not subjectively) audibly flawless playback, in today’s day and age, it’s not necessarily hifi despite whatever the price tag may suggest.
Better to consider vintage gear as just that - heritage enjoyment. Plenty of it can play splendid together and can result in Hifun - the far more important abbreviation to pursue in all this, eh!? 😉