It sounds as though the hotel was understandably quiet the first week of the New Year.
I've stayed at Hilton Munich Park several times and had no complaints about the guestrooms (outdated bathroom tiles aside), executive lounge, or service. As for your specific observations:
- In my experience, many European hotels equip guestrooms with an electric kettle and instant coffee rather than a drip machine.
- I've always found the executive lounge well stocked and serviced by European Hilton standards. Considering that the wine refrigerator was locked, perhaps you visited before/after the published evening reception hours?
- Public transportation to/from MUC is simple and inexpensive, but no one would reasonably suggest this property as an alternative to an airport hotel.
Hilton Munich Park is not perfect, of course, but if you feel it warrants just a 3 out of 10, I fear your standards are impossibly high.