I've been asking myself why continue to bother with it. I'd be much better off in SPY.

That sentence is often improved by adding:
"...for results ending right now".

In strong bull markets, especially those during which very-large-caps are in the lead, doing anything but cap-weight indexing looks foolish. The numbers show it. Only the Bogleheads look good. We have been living through such an era lately.

But that does not describe all market conditions. It's not fair to say that "what goes up must come down", but multiple expansion is a reality, and sometimes multiple contraction is a reality too, so it's not an entirely false saying either.

Since the recent bull market has been so strong, valuations are stretched by almost any metric, so it seems likely that at some point cap-weight indexing will be a very bad idea. Maybe soon, maybe not, but definitely at some point. To get a decent return, or even a less-worse return, will then require other strategies. Assuming one wants to have a less-worse return, of course.

Definition of a secular bull market: indexers look smart.
Definition of a secular bear market....?

Jim