There is still a way to select a different version of a starter template.
In Step 2 of the Create New app flow, you have a link to 'Discover community starter app',
this brings you to the overview of all available starter templates. Select one Starter template, and select the 'Releases' tab. There you can choose relevant release versions. And use the 'Start with app'
Unfortunately this was a deliberate decision by Mendix to encourage people to try out the newer versions. As a workaround, I would recommend downloading the Mendix version that you want to create your app for, and creating your new app from there. This still allows it to be created in that specific version.