I've used Leo since around 2015, at which the project was 18 years old, not sure how old the actual implementation was at that point. But the interesting part even back then was how few in this app actually worked, and how many errors it had. The amount of data loss I had in the beginning was interesting. Notable are also all the "creative" poor solutions for certain features. And till this day I will never understand why the file-menu does not follow the established culture, and instead is all according to "gut-feelings".
That said, it has become a bit better in the last years, at least the data losses have been mostly fixed, and some creative solutions have been improved. But I've seen in the 5 years I used Leo many new people coming and going, and I don't think that will ever change. The project itself is much its own greatest obstacle for success, IMHO.