You are mixing up issues here. I don't think cookies are non-free.
Sorry for that.
They are not essential for the functionality of the form as you
already explained. You can block them easily.
And it is Free Software, so anyone is free to host an instance
without google analytics.
Yes.
My main point is that the central server install Google Analytics cookies in the browser. So beware. I won't prefer that central server.
I don't think it is a good idea to lose nuances and give same
priority to all the problems in the world.
The main nuance which matters here, I think, and which makes this software different from Google Forms is that you have a defence so that you can avoid the data entered to be send to Google.
The following is not related to this case but it is my general remark on the nuances statement:
We can decide for ourselves which nuances matter for us.
For example, free software movement does not consider some non-free software as more ethical than the other non-free program. It considers all nonfree software as equally unethical.
Let me quote https://www.gnu.org/philosophy/free-sw "While we can distinguish various nonfree distribution schemes in terms of how far they fall short of being free, we consider them all equally unethical."
There are nuances in how much freedom proprietary programs give but we don't think those nuances are worth considering. Any of you can decide if you would like to consider those nuances--that some proprietary software gives more freedom than the other proprietary program-- in your personal life. Depends on the case and the person's priorities.
If I avoid using messenger systems which make phone number as mandatory for the service, I don't want to consider further nuances before rejecting them. You don't have to see that way. You can consider further nuances before making a personal choice.
Now in the case of Kobotoolbox, software freedom nuance(I think) matters and gives us a real defence against tracking while Google Forms does not.