You should look to niche down to build a Calendly that is 10x better specific group of users - it is going to be hard to make scheduling 10x better for a general audience.
Ex: I've been pretty happy with https://zcal.co which seems to target people who are looking for more personalization of invite links (I've mostly been using it because it is cheaper than other options for all the functionality I care about).
Ex: I've been pretty happy with https://zcal.co which seems to target people who are looking for more personalization of invite links (I've mostly been using it because it is cheaper than other options for all the functionality I care about).