Writing software goes a lot better if you plan first.
Software architecture is important. If you just code randomly you’ll end up with a jumbled mess with lots of redundant parts that end up doing similar business functions in a different way.
Get others involved when you plan. Never develop a plan independently. This should always be a group effort.
If you fail to plan, you will need to a ton of rework, both in the short and long term. You’ll create a mountain of technical debt. Don’t be that guy.