Limiting the amount of resources spent on the bullpen is pretty common around baseball. Bullpens are super volatile and unpredictable. You see it all the time where teams think their pen is a strength going into the season, only to find out it's a weakness - and vice versa. The pen is also the most likely place you discover an uncovered gem by throwing stuff against the wall. Annually, there are more surprise breakout players in the pen than any other position in baseball.
When teams invest more into the pen, than that almost always comes with less investment in other areas. You can't just say "if he knew how to build a pen, we'd have won the WS" because maybe assigning more assets to the pen means we don't have Barger, or we didn't extend Kirk, or we don't land Bassitt or Bieber. You can't just look at it in a vacuum like that.
Positional players and/or starters are often more consistent performers. Personally - if I have to choose, the pen is one of the last places I want a lot of assets and resources spent.
That said - Atkins has shown a willingness to add to the pen when it makes sense (as was noted above).