Are you going to put up with accountability that you might have misconfigured something and it allowed attackers to scam people or serve porn?
You are perfectly sure that you are going to keep your small site updated all the time and you won't forget about it?
Because that is where it is going - it is not just code that can be vulnerable - but also combination of different software, combination of configurations. If you install 2 applications they might interact in a way that makes your system vulnerable.
Software is infinitely complex we can cut down complexity but then anything that is useful and complex will cost a lot more.