The good thing is that with ansible-core 2.20+, it will tell you when you run the role/playbook/task file which places use the old way to access facts. So it’s not that hard to find these places. Or at least most of them…
The bad thing is that you have to pay careful attention if you’re using plugins such as community.sops.load_vars, since you should better not change “facts” they created since they will change to real variables once ansible-core finally allows it (hopefully in 2.21). It would have been nicer if the deprecation would have only be done after allowing plugins to set variables (and not just facts)…
Maybe the idea is to make it easier to distinguish between facts and variables. Right now their relationship is quite confusing. (And ansible.builtlin.set_fact’s name implying that it “sets facts” while it usually sets variables is not helping…)