Did you set Wireguard interface IP?
Try to ping (from Mikrotik) other side of VPN using internal wireguard IP - in my case remote (VPN) side is 10.13.13.1, my local side (Mikrotik) is 10.13.13.3.
You need to add NAT for sure:
/routing table add fib name=via-wg // create new table
/routing/rule/add src-address=192.168.88.0/24 action=lookup table=via-wg // route traffic from whole LAN, assuming that you have default config
/ip firewall nat add action=masquerade chain=srcnat out-interface=10.13.13.3 // Mikrotik Wireguard interface IP
/ip route add gateway=10.13.13.1@main routing-table=via-wg // VPN Wireguard remote IP
And for some reason, fasttrack need to be disabled. I’m still looking why, you can check on my thread: http://forum.mikrotik.com/t/ros-7-1beta2-routing-via-wireguard/144669/1