> Every struct or bare fn now needs (2) fields/parameters by default.

Storing interfaces a field in structs is becoming a bit of an an anti-pattern in Zig. There are still use cases for it, but you should think twice about it being your go-to strategy. There's been a recent shift in the standard library toward "unmanaged" containers, which don't store a copy of the Allocator interface, and instead Allocators are passed to any member function that allocates.

Previously, one would write:

    var list: std.ArrayList(u32) = .init(allocator);
    defer list.deinit();
    for (0..count) |i| {
        try list.append(i);
    }

Now, it's:

    var list: std.ArrayList(u32) = .empty;
    defer list.deinit(allocator);
    for (0..count) |i| {
        try list.append(allocator, i);
    }

Or better yet:

    var list: std.ArrayList(u32) = .empty;
    defer list.deinit(allocator);
    try list.ensureUnusedCapacity(allocator, count); // Allocate up front
    for (0..count) |i| {
        list.appendAssumeCapacity(i); // No try or allocator necessary here
    }