Saying that refers to not going overboard in solving a problem when a simple solution exists
'Don't use a sledgehammer to crack a nut.'
To use 'a sledgehammer to crack a nut' means to use disproportionate force or expense to overcome a minor problem. (The Phrase Finder)
I like
Don't use a cannon to kill a fly.
- “Don’t overthink it.”
- “Don’t make a mountain out of a molehill.”
- Possibly “Don’t use grenades to kill mosquitoes.”
I’m pretty sure there are many, many more.
There is an acronym KISS, which stands for keep it simple, stupid often applied to this type of situation. [Wiktionary]
One example: Don't reinvent the wheel