"it seems that lack of soul or engagement is a common theme more so than other critiques"
Everyone describes what they hear based on their own impressions, so I can only speak to my impressions of the Class D Acoustic Imagery Atsah monoblocks, that I owned for over a year. Those amps were built using the very same Hypex NC1200 modules used in the Merrill VERITAS monoblocks, and in Bruno Putzeys’ own Mola Mola Kaluga monoblocks.
As I wrote in these forums in 2021, the Atsah’s sounded, “dry, or at least dry’ish and lacking in that last touch of "realness," which better amplifiers are able to convey.”
A similar impression was conveyed in a review of the Mola Mola Kalugas, where the reviewer for “Mono & Stereo” wrote, “All notes were there but the illusion of musicians standing in front of me wasn`t convincing at all. The music didn`t sound inviting and involving, it was just… there. The emotional content was missing and the tonal colours were somewhat bleached. For lovers of analog reproduction and concert goers the sound could also be quite fatiguing and plain boring."
To me, those impressions are mostly consistent with the current comment,
“lack of soul or engagement."