It does depend on how hard the SET o/p stage is being asked to work.

Very sensitive speakers (presenting a benign load) used in conjunction with a SET amplifier can allow an well designed output stage to operate with sufficiently low levels of distortion.

However, many SET amplifiers are heard when coupled to inappropriate loudspeakers and can sound very poor.

It can be a good thing to have simple circuitry with few gain stages. It can also be a good thing to use speaker drivers in such a way that they don't have to move very far to generate a given spl.

I suppose it depends on how one feels about the use of nfb, op amps etc. If they are considered to be perfectly transparent with no audible side effects then SET's and suchlike appear foolish & unnecessary. If, on the other hand, a person feels that Op Amps, negative feedback (& active filtering using feedback) along with complicated high power amplifiers & long throw drivers have no place in audio systems and spoil the sound of music played through them, then that person will doubtless disagree.  It takes all sorts.

Some people prefer the sound of SET amplifiers and efficient speakers. Others prefer the character & colouration added by a deck like the LP12. Others might say that digital amplifiers incorporating room correction are the only way to go. Telling any of them that they are wrong or that they are not achieving 'hifi' will not alter their perspective one iota. They will say that music reproduced in this way sounds more like and gives more the feeling of music as they hear it at a live event.

Oranges or apples. Which is more fruity?