My gut feeling is that having those expendable scouts and soldiers on your team is what makes the game dynamic and exciting.
They can afford to make the risky plays because they come in duplicate. Only having one of each sounds like a total grind where pushing becomes less and less the favourable option.
Suddenly when half your team is slow as fuck aggressive holds become a huge gamble, because the window of time for transitioning between good positions is even larger.
Your only soldier died? OK I guess we can't control a choke point or pressure the enemy medic for 20 seconds. What is our play? Hold or retreat.
Your only scout died? OK we can't chase down weak players or backcap for 20 seconds. What is our play? Hold or retreat.
Even though we have two scout and two soldiers all four of those players tend to play very distinct roles in the prevalent passive/aggressive pocket/roamer setup. When you start replacing those roles with the ridge utility classes a lot of your teams decisions become binary choices because they are painfully ineffective in the majority of situations.