It's sad to see an enthusiastic article about a dying product range. I can't recall seeing a Reg article about the Moto Mod system since its launch.
I've suspected from the beginning that unless Moto licensed out their physical connector to other phone vendors the critical mass of developers and users ( to share development and tooling costs) just wouldn't be there.
Project Ara was to time, LG's modular system was just daft, but the Moto Mod system seemed ideal - offering genuine usefulness (especially hot swappable batteries) with no big downsides. For sure, it means that once you'd invested in a few Mods you'd be tied to phones of a certain size, but many users have already settled in a phone size that suits them.
If Moto had sold all the Mod phone range in the UK and every commented here who stated they just want a phone with swappable battery had bought one, they might still be a growing concern.