Thanks! I guess instrumental covers like these mostly make sense to the listener only when they know the original. Recognition and imagination of the original vocals play a big role.
I didn't know the cover song by Agnetha you mentioned.
Regarding the question of comparing the old classical Abba songs with the new ones, I think a comparison is difficult. Some critics wrote the new album was "ghost music" like coming from 1983 - but others say, no, it actually does NOT sound like Abba 1983, and I think they are right. Not just due to the riper voices, also the arrangements and melodies of most songs are somehow a bit more abstract, less simple and straight-forward than those classics. But I think this is a natural consequence of the 40 years that passed. The typical Abba sound, especially in the segments of multi-voice overdubbed vocals, is there, and it's still a miracle to me.