yes. Sometimes blocks are much better.
Putting up a block on movement allows you to prevent someone from running away while you shoot the crap out of them.
Aspects are great because, if they're sticky, they last the whole scene but they are dependent on compels. For instance, someone is running away, but they have a 'bound by vines' aspect on them. You invoke it to prevent them from fleeing. This instigates a compel which they could pay off and run away. Blocks are great but only last 1 exchange + duration (if it's from a spell).
For you second example, you'd probably still need to determine what action you are blocking. (attack, maneuver, movement etc..) but blocks can be pretty flexible so your GM might determine that an attack is blocked because they can't target and then determine that their movement is blocked because they can't see where they're going. The problem with this kind of block is there are more things that can break the block. The more things a block prevents, the more things you can do to overcome it.
So, a block on attack can only be overcome by attacks. A block that prevents 'everything relying on sight' could be overcome by any of those things: sprinting, attacking, investigating etc...
Although some people would argue this kind of block would work like a veil and would, therefore, only be overcome by perception checks like investigation and alertness. I suppose it depends on your GM.
