Installed with default settings, GA4 mostly measures pageviews. The value lies in what you set up yourself.
The most common mistake is a thank-you page that counts again every time it is reloaded. Your conversion rate then looks too high and you are steering on a number that does not exist. We check every measurement for double counting before anyone steers on it.
If ten events are marked as conversions, the system optimises for everything at once, and so for nothing. Mark what makes money; you still measure the rest, but it does not count as a goal.
By default, GA4 keeps user data for only two months. If you want year-on-year comparisons, you need to change that or export it — otherwise the data is gone before you need it.
A question or project on this topic?