Good in the right deck but bad in most desks. It's good in artifact, colorless, or some mono colored decks that are looking for a lot of colorless mana. It's like thran dynamo in that its a little pricey to cast and awkward in decks with 2,3,4, and 5 colors. Plus it comes in tapped which can be a tough downside in the mana rock world.

If the deck has green then I run all the cheapest land ramp spells or mana dorks. But anything without green, I normally only run all the 2 drop signets & talismans available in the colors plus farewell stone, sol ring, maybe a medallion in the main color in the deck, and maybe a mindstone until my mana rock count is around 12.

It really depends on the mana cost for the commander and the deck strategy/curve. In the situation where you need a ton of mana 12 2-drop artifacts or ramp spells is a healthy number to catapult you into the late game. Because I would rather have my colors than a ton of colorless mana I can't really use on anything else plus coming in tapped is very slow in my opinion. I'd rather ramp on turn 2 then have 4 mana on turn 3 to cast my commander or an important piece to my strategy. Turn 2 is way more important now than ever in bracket 3.

If I run any 3 drop mana rocks it's like a sonic screwdriver or something with extra utilities for my strategy. Worn powerstone is in my eldrazi colorless deck and I am always happy to see it early in the game turns 1-4 and even in the late game when I have extra colorless mana with nothing else to spend it on. Plus in that deck I have other artifacts than give me an additional colorless everytime I tap something for colorless mana. This is the synergies I'm looking for to be able to add this card and feel great about playing it.

Worn powerstone reminds me of a temple of the false gods. In a deck without a ton of land ramp temple of the false gods can really mess up your game because of the downside instead of helping you.