It’s an alternate to legacy because of the cost of dual lands and other reserved list cards such as Lion’s Eye Diamond, Mox Diamond, City of Traitors, etc.
The difference here though is there are very few decks in legacy that flat out require reserve list cards like vintage does and there are lists that function perfectly well without any (Burn). The dual lands are probably the most ubiquitous cards from the RL and they exist in multiple lists, but outside of that most of the RL cards are limited to 1-2 decks. The ones you mentioned are probably the most prominent after the duals and the only decks playing them are either problematic to begin with or just people trying to show off their wallets.
Now personally I think if the problem you want to fix is LEGACY, then the better route is to just ban some stuff from Legacy. Give every dual land the axe, make people play shocks with their fetches and force them to think about the mana they play. Ban LED, no deck that plays with it does anything healthy in the format, let it be a vintage and cEDH staple. I don't think leaving City of Traitors in the format is really the thing that is oppressive to people joining your format.
I don't think WOTC trying to juggle another all sets eternal format when they cannot manage 1 all sets eternal format is a great solve for anything.