Urza's Saga is a powerful land. I mean it's bad to drop on turn 3 or 4 or later because it won't have time to affect the game too much. But as a turn 1 drop it's great. If it finds a mana rock (for example
Sol Ring in EDH) it will replace itself or produce a net gain in available mana. I think it's a powerful land not to be underestimated. Perhaps cEDH won't play it but lower power decks will definitely be interested in it.
Some cool things about it:
A saga has the lore counter placed on it as a turn based action that can't be responded to. Then the appropriate chapter triggers, which can be responded to. The Saga won't leave the battlefield (as a state based action) until the trigger has fully resolved. This means that A) you can float one mana from the land, then go find your
Sol Ring and have three mana available to you on that turn and B) you can remove counters from the Saga with e.g.
Clockspinning,
Hex Parasite, or
Power Conduit. This will effectively remove a lore counter from it preventing it from being leaving the battlefield but chapter III will still resolve. This is because the Saga's trigger will check the number of lore counters
on resolution for whether it will go to the graveyard, not when the chapter triggers. Which chapter triggers is checked at the time when the trigger is placed on the stack, hence you can repeatedly have the same chapter trigger. Rinse and repeat for a free tutor on every turn of yours.
If you can get that ball rolling you're in a good place considering the
abundance of cheap mana rocks and combo/synergy pieces. I can see this being relevant in many decks, not just ones that proliferate.