I definitely encountered this second-system effect recently. I have an app that works well because it was written to target a specific use case. User (and I) wanted some additional features, but the original architecture just couldn't handle these new features, so I had to do a rewrite from the ground up.

As I rewrote it, I started pulling in more "nice to haves" or else opening up the design for the potential to support more and more future features. I eventually got to a point where it became unwieldy as it had too many open-ended architectural decisions and a lot of bloat.

I ended up scrapping this v2 before releasing it and worked on a v3 but with a more focused architecture, having some things open-ended but choosing not to pursue them yet as I knew that would just introduce unneeded bloat.

I was quite aware of the second-system effect when doing all this, but I still succumbed to it. Thankfully, the v3 rewrite didn't take as long since I was able to incorporate a lot of the v2 design decisions but scaled some of them back.