Creating a go engine used to be a huge effort. After a basic program structure was in place, a lot of tuning was needed.
Since Deep neural Networks were adapted to go, creating a new engine has been a lot less work.
And since the AlphaZero go engine training technique, creating a strong go engine is not so much work, but awfully lot of GPU computing time.
So currently I am in progress of doing new engine for Hactar. This has progressed really well; I hope to be able to publish results really soon (still, do not hold your breath). The main challenge is to reduce the needed GPU time to something reasonable.