Yeah but the reason the format should exist is to offer players a non-Standard format that doesn't have the barriers to entry that Modern has, just as Modern was created to satiate players who couldn't break into Legacy or Vintage. At some point cards just get too expensive or the supply gets too limited to support new players entering into the Post-Standard environments.
And in a couple years, it will have just as big a barrier of entry as modern does, and players won't be able to break into it either. It's impossible to keep the barrier of entry to an eternal format low long after the staples are out of print. The concept is built on the selfishness of current players who don't care if the last generation's modern collections retain their value, but also want the next generation of players to be forced to buy into frontier so that their collections stay valuable.
It's also completely arbitrary where they picked. Like I think Magic Duels (very bad game; good idea though) made a good decision by separating at the literal Magic Origins set to start over with the new universe. It makes sense from a flavor standpoint as well as sort of a power one. Frontier has like 4-5 more sets in them and is a completely arbitrary cut-off b/c someone says so.
To be blunt if they want a good eternal format they have to make a good digital version of MTG that doesn't become insanely expensive to buy into later (MTGO) or a big mess (Duels). The easiest way to remove the barrier to older formats would be to have a F2P game that exactly mirrored paper magic but kept the digital store open forever and removed the player economy and second hand market.
Such a thing will never exist b/c it could feasibly compete with paper a little and that can never happen.