It really was not that good. Only his aquisations of Rich Hill and Shark amounted to something. Of the whole nothing was remarkable.
2003: They picked Harvey #3. Nick Markakis went the next pick as a LHP and converted to RF...
2002: Matt Cain went 4 picks after Brownlie.
2005 Theo pick Elsbury 2 picks after the Cubs pick Pawelek.
2007 Cubs have #3 pick. Matt Wieters goes 2 picks after. Bumgarner #10. Heyward 14, Porcello #27
2010: Hayden Simpson #16. This had to be the crappiest draft ever... Mike Foltynewicz 2 picks after. then Christian Yelich Aaron Sanchez Taijuan Walker sad really.
2011 is when he finally did something right Javier Baez. But he passed on Cory Spangenberg, George Springer Sonny Gray. So there is still some stuff to be said here.
Theo isn't perfect either.
2012: Picked Almora but could have go with Giolito who was seen as the early #1. Fell to 16. Wacha went 19. Cory Seager #18. So drafting Almora was pretty questionable.
2014 could have drafted Nola vs Schwarber. I love Kyle but Nola is TOR while Schwarber is showing platoon splits.
Honestly don't think you have a firm grasp of how teams actually approach drafts and the reason Hendry failed. You don't fail in the mlb draft because you "take bad players." Everyone takes bad players. You fail because of HOW you draft. Hendry had an over reliance on HS picks high in the draft. If you're going with that approach you have to understand what you're doing. By their very nature those players are boom or bust. That's how you can get the best pitcher of this generation(kershaw) with the 7th pick and the best hitter of this generation(Trout) with the 25th pick.
If you then contrast that with the drafts that obviously have done well at the top under theo and you see a polar opposite. In fact, I'd argue that the cubs in particular are good at finding college players with warts. People didn't think Schwarber could play a position. Happ didn't fit easily into a natural position. Bryant was a question of staying at third that likely stopped him from being a top pick.
As for "mistakes" theo has made, Almora and Schwarber weren't mistakes. First off as I recall Giolito had an arm injury for a guy who was a HS pitcher. That's about as risky as a prospect as they come. You don't build a farm system with that sort of gamble. Almora wasn't a tool shed that some top 10 picks were and he wasn't a college guy but he's about as safe as picks come for HS bats. First of all, CF is the most difficult position other than possibly catcher to fill. Most MLB CF are poor defenders. Last year there were 9 CF who had a positive UZR/DRS among players with qualified innings. We've known all along Almora was a gold glove type defender and obviously this year is proving that. The question was how much can he hit? What we knew even early on in his career is that Almora has elite contact. He doesn't k much. Again, that as metrics go for success is an incredibly safe play. The main questions were does he develop power and can he learn to walk more.
As for Wacha/Seager, Wacha wasn't thought of as an elite level talent either. The thought was he resembled Jon Garland. Saying Almora was a mistake because of a guy who has a 3.83 career ERA with 7.97 k/9 and 2.94 bb/9 to me is pretty silly. That's basically a #3 starter or probably worse on a contending team. As for Seager, I mean he went to the 18th pick. The question on him at the time I believe was whether or not he stayed at SS and I think he had a fair amount of swing and miss early on. Good for the dodgers to find a guy that late. But picking him out is the definition of cherry picking. Among HS bats mlb.com thought was better include D.J. Davis, Gavin Cecchini, David Dahl, and Courtney Hawkins. Davis went 17th, Hawkins went 13th, Cecchini went 12th, and Dahl went 10th. Russell also went ahead of Seager at #11.
As for Schwarber, you're ignoring the reason he was picked. The cubs thought he was the best bat in the draft. But the rest of the industry didn't. MLB.com had him as the 16th best player headed into that draft. The reason the cubs took him aside from liking his bat was it allowed them to use more money later in the draft on Cease. Schwarber signed for $3,125,000. Aiken didn't sign. Kolek the #2 pick signed for $6,000,000. Rodon the #3 pick signed for $6,582,000. Nick Gordon the #5 pick signed for $3,851,000. Alex Jackson the #6 pick signed for $4,200,000. Aaron Nola the #7 pick signed for $3,300,900. It's not until you get to Kyle Freeland the #8 pick who signed for $2,300,000 that you see someone signed for less than Schwarber and even if you get down to Trea Turner with the #14 pick he signed for $2,900,000. In other words, they likely saved close to a million in draft slot money vs a similarly slotted player like gordon/jackson.
As for rather having Nola, he's not an ace. He wasn't then and he isn't now. An "ace" need three plus pitches at a bare minimum and the scouting on him coming into the draft was he had a plus fastball/change and great control. He's a mid rotation starter who would move quickly because A) he was a college arm and B) he already had great command. If that's what you get out of a top 10 pick you're probably happy but for the #4 pick in a draft that isn't high upside.
As for Schwarber being a "platoon" guy, think that's also wrong. He's got issues with LHP no doubt but you have to remember he's only had 153 ABs vs LHP in the majors and in his 49 ABs in 2014 vs LHP in the minors he hit .265/.368/.531 vs .318/.403/.573. So there's certainly a BA gap there but the walk rate and slugging are likely the save if his average was better. In 2015 in AAA he hit .379/.419/.759 vs LHP vs .290/.389/.516 in 29 ABs. Last year he hit .353/.421/.882 vs LHP and .333/.520/.556 vs RHP in 17 ABs. So in essence, you're looking at a guy who largely dominated minor league lefties over 95 ABs. In total that's 248 ABs vs LHP since he was drafted. Obviously MLB pitching can exploit flaws he has right now. Do you know how long it took Rizzo in the majors before he finally started hitting LHP? In 2011 he hit .172/.273/.345. In 2012 he hit .208/.243/.356. In 2013 he hit .189/.282/.342. That's 352 ABs in the majors. And unlike Schwarber, Rizzo had a lot more time in the minors. He had 479 ABs vs LHP in the minors before he finally stuck in the majors in 2012. In other words, that's 831 pro at bats vs LHP before Rizzo finally clicked vs LHP. And obviously Rizzo is probably a borderline hall of famer at the moment assuming health going forward.
Simply put, would you rather have Schwarber and Cease or Nola? I don't think that's a tough question. And given the cubs knew Cease had an arm injury they could likely surmise that he wasn't going to get drafted high enough for most teams to pay him properly. So, if they also liked Cease a lot which.... i mean they drafted him so of course they did.... you are nailing two birds with one stone. And while Cease is far from a guarantee, his upside is more than Nola's was. The reason Nola went so high wasn't talent. It was because he was a safe pick.