You can't use spaces to align because you can't assume a monospaced font will always be used. You can't use tabs either for that matter. If you need structure, use the language's punctuation and line breaks.

I can and do assume a monospaced font when using spaces to align code. Folks using variable width fonts will get what they deserve.

You can use tabs, that’s exactly their role, but only in theory since in practice elastic tab stops that would work with proportional fonts aren’t implemented anywhere in code, only word processors