I'm pretty sure there should be english announcements. Maybe they were broken. You also get this information via the displays on the wagons and on the screens inside. There is a bus/train from Freising to the airport every 10 min that takes 15min, so you are not trapped there for hours. Google maps also has all the public transport connections available for navigation. That it does not support certain things like train splits or instant train changes is not DBs problem.

The preferred way to get to the airport is via S8 (not S1). Idk how one could push/guide people more to take this one. S8 does not split and it definitely has announcements in english. They also prioritize keeping S8 running above anything else.

I'd also recommend buying tickets via app, not via ticket machines.