Second that!
Just compare the regular (non-discount) prices of the ETS2-DLCs with the price tag on a proper FSX payware addon (of which I have tons of):
Flightsimmers are used to pay not less than 20 or 30 EUR for a decent midsized single airport addon or an average addon aircraft. So there's no reason in complaining about the DLC requirements - set aside the absolutely comprehensible technical reasons concerning the DLC assets needed for ProMods to work with!
Both ETS2 and FSX do work without these addons, but in order to get some luxury - you have to pay the price.
There's no economy cheat mod in real life!
Cheers,
Markus.