A good goalie and a good defense will keep you in games but you need consistent scoring to succeed. Either from a mid or a couple of strong finishing attackers.
I know there are some exceptions, but at this age, I feel like middies score 70% of the goals for teams,
You are correct. You want your race horses at midfield and your true finishers at attack. At a young age the finishers and best athletes are generally midfielders but as they move up in age and play more of a settled offensive game, the attackers become the backbone of the offense. It's good at a young age to develop strong finishers and ball control specialists at attack so your whole offense doesn't rely solely on fast break, full field sprints to goal by the mids. This also pertains to the defensive end. You don't want mids exhausted from full field breakaways to goal and then have to try to get back on defense following a goalie save, or a turnover.
