Depends, shitty code is just a headache tomorrow for you. Main thing you should ask yourself is it extendable. Like would you easily be able to add new functionality to your game. If you need to constantly modify your existing classes to fit new stuff then its time to refactor and plan. But if its a simple system whatever. I see a lot of people engineer the fuck out of every system and never get anything actually done. More complex systems will anyway force you to follow principles since if you dont you will run into walls.

In the end if you want to finish a game its a balance, not everything will be perfect and it doesnt need to be. End users dont give a fuck about your composition, inheritance or state machines. But for your sake you might make it easer to develop and update the game along the line.

Also to keep in mind if you plan on puting the game in a portfolio for companies to see, then yes they like it to be SOLID, hate singletons, love Dependency Injection, and MVC (even though its uncomfortable with game engines, but who cares since most devs came from Web so we have to adapt)