Inning eaters have a lot of value, how many teams have (and can maintain, both health and cap wise) 3 top starting pitchers? Guys who can give you consistent quality starts (6+IP, 3 ER or less) are the key to staying competitive, along with a solid lineup and a deep bullpen.
This season there are currently only 52 pitchers with 2.0+ WAR (FG), but only 15 with 4.0+ WAR.
Nationals have 3 of the top 11 (Scherzer, Strasburg and Corbin) yet are trailing the Braves who have well know aces in Soroka and Fried.
21 of the 52 (mostly between 2-3 WAR) have FIP > 4.00.
Point is if the Phillies can continue to improve their lineup and shore up the bullpen, they don't need to add two more aces, just some solid inning eaters who are in the 3.75-4.25 FIP range, i.e., what Eflin, Velasquez and Pivetta gave them LAST season. If Howard becomes an ace, great, but they can still compete with Arrieta bouncing back, "good" Eflin, Hamels/Wheeler and even Irvin with an improved slider or Smyly with improved command.
There are maybe a dozen pitchers at best who can both give you 4+ WAR seasons and be projected to do so for 3-4 more seasons (i.e. some are guys approaching their expiration date).
Some of those 4+ pitchers are outliers,
Lance Lynn (32), 6.0 WAR, last two seasons 1.3, 2.9
Morton (35), 5.4, last three seasons, 2.9, 3.1, 0.4
Minor (31), 4.5, last two seasons, 2.5, 2.2
Ryu (30), 4.0, last two seasons, 1.9, 0.6
Which is a good reason to gamble on veteran pitchers coming back from injury.