So for the longest time the only way to block website on Mikrotik was either using the proxy feature, which does not work with HTTPS or to use the layers 7 to try and successfully block certain sites.
Well there is now a simpler way since ver 6.41 of RouterOS.
Simply use the below for example:
/ip firewall filter add chain=forward dst-port=443 protocol=tcp tls-host=*.example.com action=reject
with example.com being the site you want to block. Yes its that easy and yes it works. Screen show of how it will appear under firewall / filters.