Different Dimension cards seem niche, are they?

[K.O.2]

I haven't seen that many decent DD cards in this game, and google plus eBay don't have very good results when I searched for decks. Am I right in assuming they are a forgotten type of cards? I was trying for a couple days to get DD Dynamite to work but I might be out of luck lol. Let me know if I'm missing something.

[Zesc]

Assuming you mean D.D. and not D/D:

They are not as much forgotten as they are superseded by more modern archetypes in terms of consistency, utility and board breaking power.

D.D. Dynamite is way more fun in formats where people run Pot of Extravagance or Pot of Desires, as they'll do the banishing for you. Master Duel actually had a problem (or still has? idk I don't play MD) with D.D. Dynamite burn decks (using Lilith, Lady of Lament for consistent access) played by farm bots.

During her time, D.D. Warrior Lady was a staple of removal the way modern day Kaijus are -- hardly any competitive deck could muster something against her kamikaze into a boss monster of banishing, non-target removal.

D.D. Crow is still used to the present day as a side deck option for Spell Speed 2 removal of problem GY cards by people who looked at Dimension Shifter and decided to just not.

Return from a Different Dimension is basically Soul Charge on crack and would severely unbalance the current Metagame towards decks that banish their own monsters, should it ever leave its (deserved) spot on the banlist.

TL;DR:
D.D. as an archetype is not a viable option, but some of its elements managed to outshine it into the present day, the same way many Hidden Arsenal era Extra Deck monsters (Lavalval Chain, Daigusto Emeral, every single Ally of Justice, Trishula, etc.) outshone theirs.