What makes you think that ? I often read those sorts of reactions from Eastern Europeans (yes, yes, I know Poland is in « Central Europe ») but that's just giving us intentions we don't have. One other trope is framing the desire for a European Army as a master plan to sell more French weaponry.
Speaking from a French perspective, we'd be completely comfortable sending people fight for the sake of Poland, Romania or any EU member without too much of a second thought. We already send people to Africa all the time.
Most recently Macron's overtures towards Russia, so much so that even the Financial Times [1] felt the need the to blame it in one of its opinion pieces, and that is saying something (they generally are pretty neutral to "liberal" European leaders like Macron, even more so when they happen to be former investment bankers).
> One other trope is framing the desire for a European Army as a master plan to sell more French weaponry.
That does indeed happen and it's an active concern, one of the scandals that is about to erupt here in Romania is of the Romanian Army buying military stuff without following proper procurement procedures directly from an US company (via some Swiss and Israeli intermediaries/shell companies, depending on how you look at them). The French are fuming because apparently they were in contention for that contract, too.
[1] https://www.ft.com/content/168243c2-bac4-404c-843a-ca1f61196...
But yes, I agree (partly) with your assessment, there doesn't seem to be a lot of willingness in the Western nations to support Eastern Europe militarily (or sometimes, to even acknowledge they have a military). However, when it comes to it, they may not have a choice: an occupied Poland puts the enemy within striking distance of Berlin, so defending Poland is of strategic importance. The same applies (to a lesser extent) to Finland and the Baltic states, losing them means losing control of the Baltic Sea.
I'm not sure exactly how that would work out for Romania, from a purely West-European point of view I would draw that line across Slovakia/Hungary rather than further to the east, however as things as are now, Hungary and the former Yugoslavian nations would be a liability, so Romania may be essential to defending Italy and Austria.
That being said, I very much hope the above remains idle speculation.