It’s a fair assumption because there’s no genetic benefit to being a smart plant. Why would nature make that?
Opposable thumbs mean we have the ability to use smarts, so genetics walked the path to consciousness over many generations. A smarter horse is fine and all but not that beneficial. Being faster or stronger or sexier is probably better. Same with a plant: get more nutrients or sunlight. There are cheaper ways than being smart to do that.
Define "smart". And explain how "smart"=="conscious"
I can agree that there is no genetic benefit to being able to move at the speed animals move, because that's not how plants obtain food or avoid being eaten. Thus no need for nerves or a CNS to coordinate movement.
Take either of them and tell me why nature would have optimised for that rather than other features, like leaves. Energy isn't infinite so genetic changes optimise for easier-to-achieve ends rather than somehow jumping past all animals to evolve smarts or consciousness without evidence of many precursor adaptations.
Also why would a smart (or conscious) plant not have eventually learned to use some of that to do something that improves survivability. Like strike out, or hide down, or anything more than "somewhat grow towards the light or nutrients over time".
It's a nice fun exercise to argue with people while imbibing your drug of choice, but it's utterly unlinked to anything else we see in nature. We're not idiots, we would have seen evidence by now.
Opposable thumbs mean we have the ability to use smarts, so genetics walked the path to consciousness over many generations. A smarter horse is fine and all but not that beneficial. Being faster or stronger or sexier is probably better. Same with a plant: get more nutrients or sunlight. There are cheaper ways than being smart to do that.