So Helsinki city center is at 21km/h travel speeds, metro area at 31km/h. A speed limit of 30 km/h doesn't really affect these travel times much.

I can't find 2023 data to compare, however by other data on the net these are very common average speeds for any city in Europe even those with plenty of 50 km/h speed limits.

If more people take up public transport, bikes or scooters in fear of an average travel speed reduction of 1-2 km/h - that is a total win for everyone involved including drivers.