AST macros are very powerful. As to them being "good", that's debatable. They have advantages but also disadvantages. For one, they operate on syntax, so they're a separate metalanguage and not so pleasant to debug. For another, they are referentially opaque (i.e. when passed different expressions with the same meaning, they can produce different results), which makes them powerful but also mysterious.

What's interesting about Zig's comptime is that while it's strictly less powerful than AST macros, it can do a lot of what macros can do while not being a metalanguage - just Zig.