Many people, myself included, are still using dronekit without issue in the real world and the SITL. This topic has come up in many drone forums and it is still working fine for many.@sanperez if you are having an issue, it would be good to lay it out to see what the problems are. Indeed there is limited support, and MAVSDK might be an option. I have also played around with using the straight underlying MAVLINK protocol, but as you can imagine, without a nice API, those have presented some headaches for me.
BTW, you might now be interested in this.