It might be fast and responsive, but correct it is not. Flutter's widgets don't feel "native"; they feel like someone made a somewhat poor facsmile of the real thing because that's exactly what they are.
When you want your UI to stand out you would anyway move from native look. Flutter is very good for that.
As a user, I don't want your UI to "stand out". I want it to be consistent with everything else, so I don't have to re-learn what a button looks like. For me at least, attempts to do "branding" in this manner backfire big time - I'll recognize the brand alright, but now I have a strong negative association with it.
They are already different on each platform be it iOS android or web. Consistent for me would be same in all platform which would be a browser for most cases.
Yeah, no. I don’t want your UI to stand out, and if it does it stands out for breaking my expectations of how I expect apps to work on this platform. Every platform has a couple of things that are considered “acceptable” to customize (fonts, logos, colors) and things that are sacred and inviolable (accessibility, text editing, system API). Apps that use Flutter cannot tell the difference, and use experience suffers.
Browser apps are not native and users have accepted it. What you abt users experience might be different from theirs.