In a game like Dungeons and Dragons, which has had a strong tradition of homebrewing from the very beginning of its existence. How much do we really need to state "you can choose to change these rules"?
Because, I don't think I would see 4e as disempowering simply because it did not tell the DM, "you can change any rule in this book, these are simply guidelines" because I feel like it is understood that that is how DnD works.
If you are picking up a new game, because you were an active player of a prior edition, then you've probably been exposed to the idea. If you are a new player, picking it up for the first time and reading the rules as your only guide, the tradition is unknown to you, and so the text will dominate your initial approach to the game.
Some of this is conjecture on a fairly thin evidence base.
But surely it's relevant that the 4e DMG has a secion called House Rules. that advises GMs on how to go about changing rules and testing those rules.
Take page 42 of the DMG. It's very clear on informing the DM on how to rule improvised actions. You use the table for damage, rather than coming up with something. You give +2/-2, rather than, up to +2/-2 or "We suggest +2/-2, but it's up to you." It's very constraining on the DM. The DM has to fight the PG 42 rules in order to go outside of them, rather than being empowered to do so.
Moldvay Basic suggests resolving actions for which there are no specific resolution rules by making a d20-based stat check, or making a percentage roll. It doesn't suggest using a coin toss, or an arm wrestle between participants.
Gygax's DMG suggests a percentage roll. Again, no coin tosses or arm wrestles are suggested.
Are these failures to empower? Every game has it's own internal logic. And every RPG has some sort of logic to its resolution system. For 4e, in the context of resolving improvised attack actions,
why would a GM need to fight page 42? It offers 6 options for damage (low, medium and high for normal and limited sorts of action).
It implicitly canvasses conditions/effects (the worked example includes a 1 sq push together with damage) but doesn't give good advice on these. That was subsequently rectified by a column on the WotC website (by wrecan).
It mentions +/-2. This is the same as the modifier for partial concealment/cover. An astute GM will notice that the modifier for total concealment/cover is -5, and hence might infer that when circumstances are not just
especially (un)favourable (the wording on p 42) but
overwhelmingly (un)favourable (my wording) the modifier should be +/-5. (This would be somewhat comparable to advantage/disadvantage in 5e D&D.) Page 42 would have been more complete had it mentioned this, although perhaps the designers thought it was a good feature of design not to prod GMs too strongly in the direction of such big modifiers.
From these guidelines, a thoughtful GM or player can work out the broad parameters and tolerances of the system. That the system has parameters and tolerances doesn't seem to be a weakness of it. Every system has such things.
Perhaps one doesn't like a system where the parameters are so clearly stated. I don't really see how
empowerment helps explain what is going on there, though.
I'm also reminded here of arguments put in earlier threads that the maximum DC a GM in 5e D&D can set is 30, because that's what's mentioned on the DC chart. Whether right or wrong, that such arguments are run suggests that a GM who wants to set a DC above 30 (or below 5?) has to "fight" the DC chart. Does that mean that 5e doesn't
empower either? The implication of these arguments seems to be that the most empowering form of RPG would be one with no resolution mechanics at all - that tells the participants, or the GM, to just decide what happens. If that's what is being said, it would be clearer to get it out there in the open.