As a developer, I 1000% understand their switch to a webapp + subscription model. It makes it a lot easier to keep yourself in business and accurately reflects the amount of work/time being put into running/maintaining/updating the software.
As someone who is looking to optimize my life, getting into the subscription model just doesn't make any sense for me. I'm going to sign up for the trial to lock in the 'lifetime discount', in case I change my mind, but for now, I'm going to stick with YNAB 4. In addition to already being paid for, I understand how to use it and have a hefty history in it. My understanding is that new subscription YNAB is still under heavy development and doesn't have an import function for old YNAB data.