I also tend to put the emphasis more on figuring out whether there is actually a substantial disagreement, or just different use of terms (for things like "truth" or "reality").

Even that can fail, especially with "truth" and "reality". I have a concept behind "truth", and I'm sometimes not even allowed to use it, because the term "truth" has been hijacked to mean "really strong belief" instead (sometimes explicitly so, when I ask). I do try to get them to use "belief", and let me use "truth" (or "correctness") my way, but it's no use. I believe their use of a single word for two concepts mixed them up, and I never managed to separate them back.

Also, they know that if they let me define words the way I want, I'll just win whatever argument we're having. It only convince them that my terminology must somehow be wrong.

Finally, there is also a moral battle here: the very idea of absolute, inescapable truth whether you like it or not, reeks of dogmatism. As history showed us countless times, dogmatism is Baad™. (The Godwin point is really a fixpoint.)