I've worked with a lot of game engines, and indeed made my own engines and editors. My reason for making my own was partly that it felt like less work to write

I've worked with a lot of game engines, and indeed made my own engines and editors. My reason for making my own was partly that it felt like less work to write what I needed than to learn the intricacies of an existing engine. Also, back then the big engines didn't have as generous licenses as now. As for Unity and Unreal: I found them both very easy to get into and get productive with.