Mostly agree.
But it is an important element that France and Britain declared war without being attacked. They really did go to war against fascism. They understood the threat Hitler posed. For me, that is an important thing. The folks who everyone excoriates for appeasement were in fact the same people that said, thus far and no further.
But you are also right that neither Britain nor France was prepared to go to war for Czechoslovakia or the Sudetenland.
The phony war kinda expressed the fact that attacking France was not Hitler's immediate plan - or at least something of which Germany was capable. And while attacking Westward was one option, I think some believe Germany's (or really Hitler's) original (or at least superior) desire was to go Eastwards to establish its desired lebensraum.
France and Britain set up a line in the sand, which Hitler crossed. And so they went to war. But frankly, they were not ready to engage. Indeed, even when the time came when they did, they were not ready to engage!!
Whereas Germany was already prepared for war. And if it had originally intended to strike Eastwards, it could not leave an aggressor in its rear. And so it invaded France.
At any rate, the thing is not to fuss about how it all came about but to be happy that Hitler was defeated. We all share the spoils of victory.