To me on your screenshot the “fog” doesn’t look very thick as you still can see the cities lights from above. Maybe irl it’s really just a thin cloud layer which is bigger on your end as it cannot be measured that exact.
Keep in mind METAR is only the rough weather situation at the airport which is reported every 30 to 60 minutes - in between the reported weather may change.
On MSFS you have both METAR and live weather in place which may disagree due to data quality from time to time. Some users also got METAR bubbles visible because of this (a hole in clouds within the METARs airport radius).