Problem is, Riot wants T2 to kinda be its own thing, with Ascension and all that. They probably wanted to replicate the success of European LoL T2, the successful ERLs and EM with huge viewership, but obviously, it doesn't seem to be working outside of Japan. So importing talent is kinda natural if you are not a T1 team with an academy.
Thing you are missing is, T2 teams are not there to foster local talent. They are there to win. They are there to qualify for Ascension and find your ROI. If you win with 5 Japanese, that's a big plus (eg: FL) but it means jackshit if you don't win anything important (again, eg: FL). See where FL core is this year? You should also remember all the conversation revolving RID core last year. Giving chance for up and coming talents is a net positive for the whole Japanese scene, but no one's gonna do that in cost of their own success. Unfortunately, I think you have a wrong idea about the goals of VCJ teams.
That's why inclusion of ZETA.A and DFM.A, and to an extent academy teams in other T2 regions is so important for the Japanese scene. Because those teams are actually there to foster talent, not necessarily to win something. Also helps when teams like T1A exists that is fathering CL KR but can't qualify for Ascension, making the path for eventual VCJ representative much easier.