It's not just the energy on stage that made Dave great. It's the vision for the band and the drive he had BEHIND the scenes.
The world is absolutely filled with musicians who are absolute God-tier that toil in obscurity, but you never hear from them. Quick: Name three famous oboe players. Can you even name one? And yet the oboe is one of the most difficult instruments to play, a key piece of every symphony. The average city symphony oboeist will outplay every famous guitarist you know on insanely hard parts three days a week before an audience of sleepy pensioners, and you can't name one.
Ed and Al were going to be musicians, and they likely would've toiled away in obscurity, this rumor only a handful might have heard of, doing magical stuff in Pasadena back rooms... "What was his name, Edgar Van Hellig or something?" if it hadn't been for Dave. D
ave had the vision of stardom, saw what Ed was doing, knew it had to be HIM that got him there, and basically conned his way into the band. It was Dave who put on the glam persona, who knew all the 40s dance hall tunes, who told the band to ditch the 6-minute long metal covers for 3-minute shuffles.
When Gene Simmons funded a demo, only to try and "steal" Ed away, it was Dave that kept the band together. When the label showed no interest in that demo, it was Dave who circled the wagons, picked everyone back up and told them, we're still going to do this, we're GOING to make it.
And you gotta remember; nobody was interested in Van Halen's style. They weren't Bad Company nor the Bee Gees. They didn't have any special connections, no cousin working for a big label.
I always thought the sloppiness was a creative choice. Like the weird chords of Larry Lelonde or Mike Anthony playing the most boring basslines ever, they can actually play if they wanted to, but the style demanded something else.