Of course “poop” is solid waste matter. What you were describing is gas exchange. It is no more relevant to a question on defecation and elimination of solid waste than is breathing.
Now if you actually wanted to address how plants to dispose of solid waste then you would talk about loading up heartwood or moribund leaves with waste materials amongst other methods.
No, it *can *still be correct. In the case of your answer it was simplistic and hence incorrect.
When someone specifically asks “Do plants digest soil to obtain nutrients” an answer of “Plants take in nutrients that are dissolved in soil water” is incorrect. Plants and associated mycorrhizae do indeed digest soil, and nutrients are actively absorbed by pore proteins in addition to those that are dissolve din water.
Precisely! I gave a long answer with details, and then concluded that the metaphor chosen by the asker is correct enough for a layman. As opposed to giving no details, giving information that is incorrect by virtue of ommitting the relevant details (essentially a half-truth) and then making up a metaphor of my own.
See the differences?
Digestion is indeed involved in the extraction of nutrients from the soil by plants. Since that was the precise question asked by the OP, your answer that plants absorb nutrients dissolved in water is so misleading as to be incorrect. It is the same as someone asking if they can get burned by exposure to gamma radiation and you answering that people get burned by exposure to high temperatures. Technically perfectly correct, but so irrelevant to the question asked as to become misleading.
Someone reading your response is almost certainly going to conclude that plants only absorb dissolved nutrients and don’t utilise digestion in nutrient absorption. Hence the answer is so simplistic as to be incorrect.