Izone was one of the pioneers of the 4th generation of Kpop, one of its first groups along with Idle, Loona and SKZ. When it was sabotaged and ultimately sacrificed to the Kpop Gods, that signaled the turn into the 4.5 generation of Kpop, with Izone's daughter group Ive being the first group of this subgeneration.
Here is a rough comparison of what the gens look like:
The first half of 3rd gen (2011-2014) vs the first half of the 4th gen (2018-2020)
Exid, AOA, Apink, Brave Girls, Mamamoo, Red Velvet vs Idle, Itzy, Loona, Izone, Aespa, Stayc
The 3.5 generation (2015-2017) vs the 4.5 generation (Dec 2020-present)
Gfriend, Oh My Girl, Twice, Blackpink, Momoland, IOI vs Ive, NMIXX, Kepler, Lesserafim, Newbeans