LOT will also pay the airport fees and other things
Could you link to a source which confirms your claim about paying fees and details the "other things"? You seem to be entirely unaware that this route is already being re-started at the cost of tens of millions.
The choice in this case is:
One half-full flight a week is neither going to make or break the airport. What would help is adding more routes to destinations people actually want to go to, the kind of routes which do not need a subsidy of about 600 zloty per passenger. It's absolute insanity to pay that much!
The subsidy is 45 million zloty over five years, so nine million per year.
Nine million per year is 173,000 per week, so 86,500 per flight.
If LOT can hit the load factor they manage on their route LA-Warsaw route (73%), which is highly unlikely, given the passenger size of the Rzeszow market compared to Warsaw and the lack of onward flights on LOT to anywhere except Warsaw, on the 737 they'll use with 200 seats (actually slightly less but let's make the numbers easy here), that's 146 passengers per flight and so a subsidy of 592zl per passenger!
That money could be far better spent on other things than pointless boondoggle.
Why are two foreigners so concerned about the way LOT conducts its business?
Largely because when LOT makes a loss, we who pay tax in Poland get stuck with the bill. Just as we have to pay for the non-EU funds being diverted to LOT as a result of this insane new deal and we also need to pay for other things which could instead have been funded with those EU funds. From memory you pay zero tax in Poland.