Okay, first of all, I wasn't pointing out flaws with the shields, I was pointing out that learning to use the shields isn't as difficult as you say it does.
Our shields, while interesting, aren't all that complicated on their own. The issue is that we don't have just one part of our game causing a learning curve. A new player to our single player needs to learn the following things:
1. How the game's rules work. (Rings protect you from being hit, etc. etc.)
2. How to control the game.
3. How the controls interact with the game's mechanics, such as how rolling lets you get in small gaps, and other similar parts of how the game operates.
4. How to use the various powerups and items, such as shields, invincibility, special stage tokens, etc.
For multiplayer, there are the following additional things to learn:
5. What each weapon does and how it feels to fire each of them.
6. Judging the relative speed of your shot against the target player's speed.
SRB2 is a game of medium complexity at the core, but we have a lot of complicated mechanics on top of it that provide gameplay variety, and these kinds of mechanics take time to learn. New players shouldn't feel overwhelmed by all the mechanics at the start, so there is a limit to how much complexity can be pushed into the core parts of the game. Our basic jumping, spinning, ability use, powerups, weapons, and other core mechanics are simple on their OWN, but combined it forms something very complicated. We also tend to add stuff as time goes on, which continues to increase the complexity of the game. We don't want the player to feel overwhelmed looking at the variety of shields or weapons, but we also want enough variety to keep things interesting. It's extremely important to take a hard look at any potential additions to make sure what they add is worth the added complexity it brings with it.