When it comes to fast mana in this format you're mainly left with expensive options such as Mana Crypt, Mana Vault, Mox Diamond, Lion's Eye Diamond, Chrome Mox, among others compared to the affordable options with Sol Ring, Arcane Signet, Fellwar Stone, and the Ravnica Signets in general where they're a turn or two slower. If the expensive options were as affordable as their "inferior" counterparts assuming the Reserve List had been abolished then how bad would it end up breaking the format to where the turn clock is increased significantly like it already has with the ongoing influence of cEDH's impact on the game overall? Jeweled Lotus was in some ways a way to make fast mana "balanced" but still presented a problem within the format for those who aren't running Mono Color builds.
Also I don't feel that there's enough support for Pitch spells in the format that can deal with threats on the board when everyone's tapped out on mana let alone the incompletion of the Elvish Spirit Guide cycle which ended with Simian Spirit Guide that didn't cover the other three colors which would've gave an unnecessary boost to Esper builds so that may have been a risk the designers didn't want to end up taking. I'd probably be okay with exiling a White creature in my hand just to add W to my mana pool, however with Black and Blue that does pose a bit of a high risk. I just don't feel like it's fair for the game's Secondary Market to punish players for wanting to run fast mana when there should also be cheaper options to choose from that doesn't break the format that are just as fast.