Lots of stuff breaks only after 5 or 10 years. Because you most likely don’t have people who originally built stuff and knew why it was like that.

Then customers and market changed so you also most likely have different customers.

I had to undo a lot of over-engineering to fix performance issues that was implemented in good faith by people who ultimately left the company and they thought they did a good job future proofing our product.

I am with company from start and now it is 11 years. I knew why they built it like it was so I was able confidently what to fix. But it still took almost a year to undo stuff that was making our current customers miserable.