Well, 42 year old, slightly less competitive golfer here. But I do play well enough that I actually played a local am event last month and am planning to play a few more tournaments next year. I don’t think 4:20 is that slow, just to be clear.
I started using the alignment line on my ball this year after years of not doing it for the same reason you detailed; I’d obsess about the line and feel like I was taking forever to putt. This year I switched to arm-lock style putting to battle some issues I was having with my stroke. After a couple rounds of putting this way I talked to my golf pro and told him I liked it, but I was having trouble lining up. He told me to use the line on my ball. We talked about how I obsessed about the line when I did that previously, and he told me that it doesn’t have to be perfect, but just close enough. That freed me up and I’ve putted a lot better. In 5 tournament rounds this year, I didn’t miss a single putt under 3 feet (i.e. the ones you should make).
I think on short putts, unless the greens are extreme, you have even more forgiveness with the line because you’re close to the hole, so even if you’re a little bit off you’ll still catch the hole and the ball will drop it, assuming you aren’t just hammering the putts.
Lastly I recommend giving arm-lock a shot if you’re struggling. For me it takes all the worry out of setting up. I know that once I have it locked in, I just rock the shoulders and it’s gonna start on the line I’ve chosen most of the time. I can still make a terrible stroke (i.e. it’s not fool proof) but I’ve been way more consistent.