The last few years haven't been as productive, even discounting the injuries.
Here's the last 5 years by round...
I think this list works against your argument. It might not be as good as 2010-2013 where they hit on so many players but it's still pretty decent.
Plus the UDFA's Malcolm Butler, David Andrews, Justin Coleman, Jonathan Jones, Adam Butler, Jacob Hollister and JC Jackson all contributed to SB wins (Coleman actually didn't play in the playoffs in 2016 to be fair). Myers and Gunner have shown some flashes on offense and special teams so there's hope there as well.
1 23 Isaiah Wynn - Solid starter who has had injury issues.
1 29 Dominique Easley - Bust
1 31 Sony Michel - Solid starter
1 32 Malcom Brown - Starter
2 56 Duke Dawson - Bust
2 60 Cyrus Jones - Bust
2 62 Jimmy Garoppolo - Solid starter
2 64 Jordan Richards - Special teams (otherwise useless admittedly)
3 78 Joe Thuney - 2nd team all pro
3 83 Derek Rivers - Backup
3 85 Antonio Garcia - Nothing
3 91 Jacoby Brissett - Borderline starter
3 96 Vincent Valentine - Backup
3 97 Geneo Grissom - Nothing
4 101 Trey Flowers - Pro bowler
4 105 Bryan Stork - Starter
4 111 Tre' Jackson - Nothing
4 112 Malcolm Mitchell - Could have been great if not for the injuries
4 130 James White - Solid Starter
4 131 Deatrich Wise - Spot Starter
4 131 Shaq Mason - Pro bowler
4 140 Cameron Flemming - Solid swing tackle
5 143 Ja'Whaun Bentley - Spot Starter
5 166 Joe Cardona - Special teamer
6 178 Christian Sam -Nothing
6 178 Matthew Wells - Nothing
6 179 Jon Halapio - Nothing
6 198 Zach Moore -Nothing
6 202 A.J. Derby - Backup
6 206 Jemea Thomas - Nothing
6 208 Kamu Grugier-Hill - Nothing
6 210 Braxton Berrios - Backup & special teams
6 211 Conor McDermott - nothing
6 214 Elandon Roberts - Backup
6 221 Ted Karras - Starter
7 219 Danny Etling - Nothing
7 225 Devin Lucien - Nothing
7 243 Keion Crossen - Special teams
7 244 Jeremy Gallon - Nothing
7 247 Darryl Roberts - Special teams and backup
7 250 Ryan Izzo - backup
7 253 Xzavier ****son Nothing
You would be hard pressed to find a lot of teams a lot better. The problem is the FA defections.