I hear you. 
I’ve got literally over one thousand, I mean well over one thousand FSX missions that need to be done by the book or you fail and they are absolutely superb.
Not talking about bugs in msfs but this is one of, if not the biggest thing that’s missing from msfs content wise.
It is hands down, all the default FSX, Learning Centre and addon missions.
FSX - sold with 30+ missions
FSX Dlx - sold with 50+ missions
Then remember when acceleration came, another 30+ new missions.
Not to forget…
perfect flight: FS Apps, vol.1-3, A321 Lufthansa LH321, British Airway FOX(304 mission flights alone)
FSX Adventures: EasyJet, Aer Lingus, RyanAir, United, KLM and these are all Missions packs
Abacus: Commuter Xpress 2.
First Class Simulations: Around The World In 80 Flights .and they gave you a DC3 to do it, 2 was incl. 10C and 10E.
AirHauler… yeah, start with one aircraft and build your company… there is no other comparable product.!!
No chance, I can’t leave FSX, there’s just too many things that FSX gets right.
ATC, the flightplanner and it’s map filters, IFR/VFR/VOR, honestly the list is near endless.
I don’t want this to sound like a disrepect for the Asobo devs, but I just can’t find any other way to write/express what I feel is missing in msfs20.
For me, it’s at least another 2-3 years before we see the things I’ve mentioned.