Of course. But as a newcomer, you cannot know which one it is, and as the OP said this behaviour has a lot of chances to be perceived as invalidating. I've been on both sides of this situation, and in both cases I felt that it was almost disrespectful, it's sending the message that you don't think the team is competent enough to have considered them and carefully picked trade-offs.
When I was on the receiving side (there was a newcomer to the team doing a lot of "suggestions for improvement"), I made a lot of effort to explain the context that led to a different decision, but it was very draining and rarely the good time for it (it distracts from the conversation), it was really hurting collaboration. Eventually we had a one-to-one in which I explained exactly that, and we found that it would be much better to raise these as "can you tell me why is this one like this" (rather than "improvement suggestion" that can be invalidating), and do it in one-to-one so that it's not distracting. Collaboration was much better after that
For sure, it's great to have a new pair of eyes and you certainly don't want to tell somebody to keep their challenges and suggestion for improvement for themselves. But it doesn't mean that there's no good way or bad way to do it