Most alternatives are not made by advertising companies, but they also frequently aren't free... Rolling your own from the ground up is not necessary or typical

Most alternatives are not made by advertising companies, but they also frequently aren't free... Rolling your own from the ground up is not necessary or typically advisable when there are so many good options, including many self-hosted and open source options if you're wanting that level of control. I usually describe the cost of GA as "subsidized by your customers' data".