Well, then, if you are able to, pedal faster.
If you are not, be happy with what you've got.
If I could do 15.6mph on the commute I would not use the crap cycle route.
Imo we should have a speed restriction on Ebikes, because, although they are great for the riders that need assistance, frankly I don't see the majority of Ebike riders behaving on the shared paths if they have a chance to go faster with less effort than a non assisted rider.
Yes, there are fast riders on the shared/segregated paths, most are faster than me, some are aggressive, some are polite.
Very few though, ime of 8 years commuting, can keep the 20mph pace.
The ones that can, again ime, prefer to take the road because they have a clearer run.
The increased affordability of Ebikes give the opportunity to go fast to every Joe Blogg that hasn't been on a bike for 30 years, probably has limited bike handling skills, is not used to dogs/kids/pedestrian randomly appearing in front of him.
I don't know in your area, but here we have had to fight hard to get the segregated facilities we have.
The idea is to enable everyone, from your granny to the schoolkids, to do a bike journey in relative safety.
I say relative, because the facilities we have here are by no means perfectly safe.
No, I don't want a 20mph Ebiker on a shared or segregated path.
15mph is plenty to inflict damage, let's keep it that way.