If you've been following Magic for long enough,
you will have noticed the two-cost
mana-producing artifact design trope being used
less frequently as time goes on. It's certainly
not because the ways to design them are running
out: Pentad Prism, for example, has a very
different dynamic than Ravnica's Signets. The
Signets are, in a sense, "boring" in that they
just produce mana and do nothing else, while the
Prism can give you up to two mana and thus take
you from two to five rather than "only" four,
but has a limited number of activations. It's
usually not as purely powerful as a Signet,
though an uncharged Prism is certainly a good
candidate for use with something like Blood
Clock or Atog. And besides, sometimes when you
go from two mana to five, you don't really need
anything else, at least for a while.
