it's not possible to decide if something was a good decision or not by looking at realised performance over a short time scale.

having a portfolio that is entirely concentrated in the S&P will have less risk adjusted expected reward than one that allocates a bit in some other buckets as well (e.g. international shares). c.f. the book "random walk down wall street".

It's very hard to outdo index funds. Even Warren Buffet said as much. My personal observation over the last decade confirms it. I also trade individual stocks in industries where I understand the underlying trends, and those do outperform s&p, but I'm very much aware that betting the wrong way could instantly undo those gains. Index funds are much safer.