Although Collins 3. provides unadulterated or genuine (see #3 above),
I strongly suggest AGAINST choosing unsophisticated as a translation for German lauter.
I maintain that Collins 3. is not the meaning of unsophisticated that most English speakers understand today, but rather, Collins 1. and 2: naiv, einfältig, unkompliziert, einfach.
When used in reference to humans and social manners or matters of taste in art or style, etc. Collins 1. is spot on.
One might also add something along the lines of uncultured or inexperienced.
With reference to a technological system or process, it can mean simple, primitive or rudimentary.