The President got the invite, not Tusk.
Poland is in a weird position...
Germany has a president and a chancellor and the chancellor is the policy making position so the chancellor gets invited.
France has a president and a prime minister but the president is the policy making position so the president is invited.
Poland has a president and a prime minister and the prime minister is the policy making position so theoretically he should be invited.
On the other hand Tusk has EU connections and an experience politician (whether you like him or not) and Trump prefers those who are either big men authoritarian types (putin, orban) or gullible types who will feed his ego (like Duda).
Nawrocki (whether you like him or not) is neither an experienced politician nor self-effacing and I could easily see him getting on Trump's nerves.
My new prediction (possible solution): The split German model.
The current front line is frozen. russia is still there but is not recognized internationally (similar to the Balkan states after WWII).
Then we see which does better, westernized Ukrainian Ukraine or neo-soviet russian controlled "Ukraine"
Downsides: This will only work with NATO/US troops on the border to prevent russian incursions (because only the credible threat of immediate military force will keep russia out) and will be followed by russian style forced population transfers to try to russify the new and ever impoverished russian controlled part.