If I added a screenshot of a webpage or a link to it and asked if there is anything fundamentally wrong from a design perspective, would that be on topic? I know asking for generic feedback is probably not the best way b/c it would be too broad and may create more discussion than a concrete answer.
Ideally, you should try to make the question useful for future visitors, as brainstorming questions get usually closed.
For example, if you are having issues with the menu, instead of asking: "What's wrong with my menu?" or "How can I improve this menu" you could ask something like "How can I make web menues easier to read?", "What colors are good for menu contrast?" or "Should a website's menu share colors with the rest of the site?".
If your example is still too specific (or too broad), you are more than welcome to link it in the chat. For feedback I've also found Forrst quite useful, but there are some other sites you could try. Hope it helps :)