There is an option to change the how fast the enemy strength meter drops. In the "SetConfig" file, right near the top you can find this:
;Enemy strength, Single Match.
;The higher the value, the more enemies that need to be defeated before the round ends.
;Is not the exact number of enemies that need to be defeated. Each enemy, when defeated, drops the meter by 200 or more points, depending on their strength.
;Default is 10000. Don't set lower than 2000.
[State 191, VarSet]
type = VarSet
trigger1 = MatchNo = 1
trigger1 = RoundNo = 1 || Var(59) <= 0
v = 59
value = 10000
; ^^^^^ Change this value
ignorehitpause = 1
Change 10000 to something lower to fight less normal enemies. Take note that the Bosses & Mini-bosses take a good chunk of time to defeat, which adds up since there are so many of them. You might consider playing in Traditional mode instead. Right below the Enemy Strength setting is the "Alternate Mode" setting. Set it to 3 to only fight normal enemies; no Bosses or Min-bosses appear in Traditional mode.