I don't think it's all that bad. I think the major complaint can be distilled down to a lack of chapter opening/closing markers. Essentially, we are in a new "season" of the story which wasn't very cleanly defined. Getting married was essentially the end of the previous season and the timeskip between that and his wife being 6 months pregnant is essentially the start of the new season. Of course there is going to a "winding down" and a "winding back up again" moments and unfortunately for the reader, because they aren't so clearly defined, it feels like a long period of low activity instead of storyline grounding.
I do agree in the lack of power scaling definitions (that seems purposeful in order to give the author room to move) other than "archmage" which is simply "very powerful". I think that the author also wants to develop the world more and that's why Callum keeps on telling us how ignorant he is to things like other magic or even watching a mage attack team fight. I would agree with you that the writing isn't as good as it was at the start, but it doesn't seem "bad" yet. I think it just hits differently because the writer put more effort into certain parts of the story that ended up being so good that now we are judging the parts with lower writing investment as "bad" by comparison.
