So, let's say a 'starter' is the 8 position players, 5-man rotation, and the top 2 relievers. That's 15 guys. Now we must ask ourselves: how long can we expect these guys to be in the core of their careers, i.e. performing at the level of an above average starter -- even throwing in years of slightly below average starter. I doubt it is 10 years on average, although star players can exceed this time. I'm going to use 7 seasons. If I do that, then I need your 1 above average starter/ 1 starter/key bench guy to fill 14 spots on the roster. Assume about 30% of roster should be coming from international. So 9 of 25 man-roster and 5 of 'starters' come from international. To fill the other 10 starter spots, with a 7.5 year core career, you need to get a little less than 1-1/2 guys per draft. To fill out the other domestic-sourced roster spots, you need another 8 guys out of the draft. So you need a little over 2 guys/draft to fill the starting roster.
Then comes the depth. Counting only guys with at least 10 ABs, the Phillies had 20 position players in 2019 and an astonishing 28 pitchers who logged at least 5 IP. So that is another 22 guys in addition to the 26-man starting roster. These are perhaps 10 of the guys who start the season on the 40-man, rather than 26-man, roster and then a combination of guys that didn't quite make 40-man plus a lot of fungible minor league AAAA vets. I'll count them as needing to be home-grown, since they had to start as some team's draft choice or international sign and farm system product, with a few independent league exceptions. These guys often don't really have a core career, or are former starters past their core, but what I'll call their productive career tends to be short. I'll say an average 5 seasons or partial seasons in MLB. We have 42 depth guys, let's say 28 of them domestic. For a 5 year productive career, an average team has to produce 5 from each draft. That's all the guys you list, and more.
Btw, I don't see how you analyze a draft and skip first rounders. A good first rounder drives a draft and that is where the big pile of money goes. A good draft starts and frequently almost ends with getting the first, supplemental, and 2nd rounds right.
Look at the players you list from the 2016 draft, where we had the top slot: Gowdy (#42), Romero (4th), Irvin (5th), Dyer (8th), Stephen (11th). A lot of questions about all of them. Of the group, Stephen had the most encouraging year, with the best stats of the lot and the biggest improvement. It was Reading so offensive stats can be inflated, but he had a big increase in his walk rate in addition to the big increase in HRs and ISO. Gowdy pitched not all that much, with more walks than Ks and is Rule 5 eligible next year -- like Ortiz this winter, if the world loves him after next season, they likely can have him for $50K. Romero was better than his ERA at Reading -- Although he gave up one more run per game, for believers in the 3 true outcomes, he improved in each of the 3 -- susbstantially in BB/9 so we can label him unlucky. He fell apart in AAA, but at age 22 remains a strong prospect. Certainly the best prospect of the guys you listed, if not the best season by stat. I think Irvin will fall into the MLB depth category. He put up a nice AAA season at age 25 but faltered in Philly, because his HR and BB rates increased. Dyer looks like he can be in Philly as middle relief depth next season. Good K rate. My conclusion: to date a very weak result for the first spot in the draft. If Moniak, Romero, and Stephen continue to progress it can be an okay effort in a draft in which we had the 10 slot. It needs a huge step forward in health and performance by Gowdy to be a barely ok draft for picking #1.