Browsers block more tracking every year. Server side tracking moves part of the work off the visitor's device and onto a server you control.
What it actually fixes
It recovers conversions that ad blockers and strict browsers hide from your ad platforms. It also gives you one place to clean data before it is sent anywhere.
What it does not fix
It will not repair a bad conversion definition or a broken form. If the numbers were wrong before, they will be wrong faster.
When to skip it
If you run a handful of conversions a week, the setup and hosting cost will not pay back. Fix the basics first, then revisit.
