Which, in part, is why Taiwan (& Europe) have a hard time "struggling to recruit enough soldiers and sailors" and field a formidable army/navy for themselves.
Relying on the American military & taxpayer can afford you to do many other things (i.e. socialism).
Closer to home, we see the same phenomenon in Canada. Being under the American nuclear umbrella, the money they would normally have to spend for defense can go into things like baby bonuses and keeping basket cases like the Maritimes from abject poverty.
Its not that Taiwan was unwilling to upgrade its forces, its just been unable to obtain modern weapons. Nobody will sell them any, or components to make its own advanced aircraft.
Just look at the map and it is clear that Taiwan vs China is no contest under normal conditions.