For beginners and even rather decent players, I disagree with that. Even with some mistakes, you can still accomplish a good score (50,000 - 70,000) and even more importantly, improve your skills with the game.
For a perfect run, you need to progress fast to level 5, no deaths and catching all parachute guys. This would end up in a score way over 100,000.
Tip: Shoot the parachute guys and catch 'em, this would save you a lot of time!
Defeat bosses as quickly as possible without loosing a life.