As is typical in these threads, every runner will give you what worked for them, but we're all a little different. For every runner who has trained and hit their goals at the marathon, there exist dozens who never did in spite of best efforts.
My race times match with OP pretty closely. 19:30 5K, 39:20 10K, 1:26 HM, good performances (for an average Joe) at odd 10 milers and such, but the best I ever mustered, in 15 marathons, was 3:15 on a net downhill course. And that was an all-out effort, barely qualifying for Boston while feeling like I was on fire to get to the finish line with seconds to spare. Barely qualifying for Boston was my absolute peak, and that time wouldn't sniff a spot at Boston anymore.
I always used Daniels plans for my best efforts, although I suspect that I didn't run enough 20+ milers, because he advocated for limiting long runs to 2.5 hours for most runners if I remember correctly. Otherwise, I hit paces and distances religiously and peaked at 90+ mile weeks several times during these plans.
I have mostly gotten past the fact that while I LOVE the marathon, I'm just not that good at it. I run in the vast flow of mid packers out there, doing my best, and love it. It's possible that my body, in some way, and many runners' bodies, in some way, are just not well suited to covering 26.2 miles fast. I can run them with little drama anymore, which is nice in itself, but the good relative performance? Nope.
The most relevant bit of all of this might be that for the OP, and for others including me, if we wanted to compete against our age group, we'd focus on the shorter stuff. I don't care anymore and love the challenge of the never-quite-perfect marathon effort, so I accept that I'm a mid packer.