> So quality went up, but quantity went way down, and as a result their total effectiveness is less than the generation they're supposed to replace.
Not sure why you think this.
The 5th generation F-35 is a great airplane[1], and they've made 1300 of them since 2016.
The 4th F-16 (also a great plane!) had 4600 built since 1976.
[1] Yes, despite all the negative press and the amount of time it took to get right, it's a great plane. See eg https://theaviationist.com/2016/03/01/heres-what-ive-learned... where the editorializing is anti-F35 but the pilot who flew it only has positive things to say.