Retrologue 2 is feature rich yet easy to use, and still manageable to create 3rd party sounds for it quite easily. Not the best GUI I admit, but in case of Retrologue the purpose was usability, simplicity and acceptable gui size on current displays.
I think there is a problem with the marketing of their products, not much efforts were put to give them a wider exposure. This is getting better these days with the new, re-organized Youtube channels, they have more presence in online ads, more in-depth video tutorials, etc. HALion 6 has already a great tutorial series e.g. how to use its sampling feature.
Maybe Retrologue 3 will be handled with the same attention when its time will arrive and will be more popular not just among the Cubendo users.