This idea that pitches are "supposed" to seam then go flat then spin so that there's something for everyone...
Firstly, that's just a thing you've made up. There is no optimal Test pitch. The point of Test cricket is its richness and diversity.
Secondly, that kind of a pitch isn’t as fair and balanced as you think it is.
On a seam then flat then spin pitch, the team batting first gets the better of the spinning conditions and the team batting second gets the better of the seaming conditions.
That’s completely fine and makes for a great game, but the idea that it's some sort of benchmark for is nonsense.
Thirdly, exposing players to varied and changing conditions is half the point - but this doesn't mean that the gold standard pitch ticks EVERY box at some point over the five days.
Variety is variety. A pitch that seams throughout offers variety. A pitch that turns throughout offers variety. A pitch that seams then goes flat then offers turn only offers variety if you get other kinds of pitches too.
Now read my article about turn v deteriorationNow read my article about turn v deterioration https://www.kingcricket.co.uk/do-england-fans-think-turn-and-deterioration-are-the-same-thing/2021/02/16/
As a postscript to this, I think cricket lacks the language to talk about turning/wearing/deteriorating pitches properly.
A pitch that wears and then turns is generally good. A pitch that deteriorates so much that it becomes dangerous is not. And they are different things.
Pitches can also flatten to lifelessness as they wear. This too is bad.
Although being as some people still think 'turning pitch' means exactly the same thing as 'damaged pitch' maybe there's not much to be gained from adding more words.