There is no doubt MS changed their approach for this, their latest flight simulator.
Rather than bulid on previous versions, they decided this one will go for the visuals. From the very first announcements and trailers, this was being emphasised. To achieve this, they went to a firm with the necessary experience, who then to a large extent built the simulator from scratch. And to a large extent, they have supplied what they promised - the most visually realistic flying experience (if not always the most accurate).
But, because of this choice, many of the things present in the previous versions were omitted, as the OP and others have pointed out. From documentation of the basic sim (leaving everyone to work out how to do things either by trial and error, or by word of mouth), to main aircraft types (I loved gliders in FSX), a full variety of missions, seasons, replays etc. These were present (and for the most part working) in the FSX at launch.
They sort of acknowledged the limitations in the basic sim when they said they would support and improve FS2020 over the next 10 years, but I don’t think users realised at the time how much work there was still to do. In FSX I often got a pleasant surprise when I found something extra it could do. In FS2020, it has been the reverse, expecting it to do something, and then finding it can’t, or finding a “known bug” not even scheduled to be fixed yet.
In retrospect, I think they made a mistake concentrating so much on the scenery, at the expense of a true flying experience. At the current rate of progress, I don’t believe they will ever get all the problems fixed, and it seems they don’t even intend trying to replicate all the good features of previous sims now missing in FS2020.
But I may be proved wrong, if I wait long enough.