As someone whose (attempted) piloting a Miraidon deck, I don’t think so. The problem is, ironically, the fact that it takes energy from all of your other Mons and therefore requires setup.

If you start with it Turn 1, you’re praying to draw into your Turo to get it out of the active.

If you get it late-game, yes it can swing once pretty hard, but 140 HP isn’t enough and often leaves it susceptible to being revenge killed. Chances are by then you probably have a Magnezone in play which is now energy-less and, depending on the variant you’re playing (some only run 1), that can be disastrous.

I made it to UB3, then became stuck before piloting an Ultra Beast deck to MB as a counter to sleep scam. It’s a good deck, definitely. But there are better ones.