It's good that it works for you. Before unloading my Kindle, I was getting over 50% failures when side loading books via Send To Kindle. These were all ePubs that have subsequently worked fine on Kobo. That was completely unacceptable, and I was uncomfortable with the amount of control Amazon was exerting over the platform.

I don't hate Amazon, but I was not willing any longer to give them knowledge and control over my reading.

send to kindle is not sideloading