WotC found Breach, especially with Mox Opal, made for a combo deck that was too fast, resilient, and non-interactive, even winning on turn one
Other sweet cards that I have been experimenting with in my G/R Aggro deck are Jade Mage and Devils Play
Lurros Of The Dream-Den lets you recycle cards like Mishra's Bauble for free, giving you a free draw engine for as long as Lurrus is on the battlefield
Both apply continuous advantages to the players who has them, both apply to one and only one player, and both have very narrow interaction with other cards, only ones that explicitly mention them
A gem-mint CGC 10 Torchic sold for $117,600 in February, one of the sales that announced the Gold Star run, and raw copies have followed to $3,200 to $4,000