If you get value out of the free part of a tool, great! If not, then you get to choose to pay for the rest or not. Personally I'm happy that it tends to be the feature set I can live without that costs money. Not always, but often enough.
And if Canva decides that "I am altering the deal. Pray I don't alter it any further,"[0] what will you do then? Go and rent the Adobe subscription suite instead?
[0] http://www.quickmeme.com/img/32/32b4229145de0a2c1171b9b5757f...
There is a big difference between a one time payment and a recurring payment, especially if the company canceling the product or going out of business means you can no longer use the tool, and I honestly steer clear of those in most cases.
It's not even close. This is more akin to shareware where Bill Gates shows up at your house to collect a payment every month and formats your hard drive if you don't cough up the money.
Shareware gave you a perpetual license and control that couldn't be taken away, especially before the internet.