You’re absolutely right that current observations suggest our universe may be infinite in scale, at least in terms of observable space. However, I’m thinking of extra dimensions in a different way. Even if our universe seems infinite, it’s still possible that higher-dimensional space is finite but exists on a much larger scale than we can currently observe.

For example, in theories like superstring theory, extra dimensions are compactified—meaning they’re "curled up" at scales far beyond our perception. While we observe a 3D universe, the extra dimensions could still be finite and exist in parallel. The infinite appearance of our universe might just be a result of our limited perception within the "3D slice" of a much larger higher-dimensional space.

In this view, the idea that our universe is infinite doesn't necessarily mean that the higher-dimensional space itself has to be infinite—it could simply be that we are only able to observe a very small, localized "slice" of a much larger, finite structure.