Generations in Kpop, as with many things in Kpop is 'fuzzy', there is no quantifiable definition and it is all popular perception.
Every debut, gets a chatter of a new generation or 0.5 generation being born. But give it a few months, then we know how relevant such claims are.
It is only in retrospect can we actually judge the start of any generation.
And that start is always has been with a significant group making music and records, which are different from the prevailing trends.
Then groups which have debuted around the same time are grouped in as a generation. Even if the other earlier debuts later achieve greater popularity, they still join that generation.
In retrospect.
2nd Gen's defining group was Sonyeoshidae SNSD
3rd Gen's defining group was TWICE , even if BTS debuted earlier and had greater success, or BP later.
4th Gen's is NJZ- does not matter if GIDLE, Itzy, Aespa, Ive all had debuted earlier. The shift happened with the arrival of NJZ
I don't notice any discernable shift in the ground since NJZ debut.
So all the claims of 5th, 6th gen are just yawn, fans trying to partition time to claim some trivial swag.
At best the prevailing generation can be measured by the dominant acts on the K-digital charts- who are the youngest set.
It is still (G)IDLE, Aespa, IVE & NJZ
We are still only in the 4th gen. Now if say KiiiKiii or H2H manage to hit it big & have distinct sounds/styles/themes - start the new gen, then maybe 2024 debuts will be included as 4th gen.
Again it is subjective stuff and this is my take.