I just think its a weird direction for them to go, and definately not an improvement. My perception of Alfred was basically formed by Batman: TAS, and I haven't seen him act that different in any of the newer comics (I can't speak for pre COIE, but he's seemed pretty consitant from about the ninties to even now, he's not that much different Post New 52 than he was before). Heck, he's even basically the same in The Batman. He's the loyal friend/butler of Bruce Wayne, with a probable secret past in espionage and some skills in medicine and sneaking. He also has personality (this doesn't mean BTB's Alfred doesn't have personality, he does, I'm just describing what I think of as "normal" Alfred), he's not afraid to make jokes/sarcastic comments when its called for, and he'll disagree/argue with Bruce when he thinks he needs to. He isn't a threat to basically anyone unarmed, but he's not a pushover and you have to be careful of his shotgun (which I always thought was kind of funny, Bruce hates guns but Alfred has a shotgun in several differnt stories, both comics and animated). Stuff like that is Alfred to me.
Muscle bound action hero Alfred is definately not a change that needed to be done or that is particularly interesting. Like I said, it doesn't ruin the show for me, but Alfred is definately one of the shows obvious flaws. He's still better than Michael Caine's Alfred (who might be my most hated character from those movies, I can't even watch Caine in other roles at this point without wanting to see him get beaten up) but since I don't think a worse Alfred than Caine's is possible, thats really not a compliment. For the type of Alfred he is (super muscular master of hand to hand combat with generic personality of those kinds of characters) he seems to have been done as well as can be expected. Still, I wouldn't be sad if his leg injury somehow lead to him losing 70lbs of muscle and forgetting his fighting ability.