From my personal experience, it's quite good. It gets free priority Grassy Glide when it automatically sets up Grassy Terrain, making it a very potent threat. It also gets access to Swords Dance, and +2 Grassy Glides in Terrain are terrifying. If you give it a Grassy Seed, for example, not only will its Defense be boosted, but Acrobatics starts doing massive damage as well. It gets Drain Punch as a reliable form of recovery, which also hits things like Pawniard, which it can't reliably hit otherwise. You can also get free chip damage with Fake Out, breaking Sturdies from Magnemite and Onix. It gets U-turn to pivot, and Wood Hammer for greater damage than Grassy Glide, at the cost of no priority.
So from my experience, Grookey is a very solid Pokemon in Gen 8 LC.
Hope I helped!
