In order to make a difference, the added capacity has to be meaningful to guests. That's where something like LMA almost certainly comes up short. If we view this from an "all things being equal" perspective, 5000 people sitting in the LMA theater means fewer people waiting for Rise, Falcon, Slinky, etc. But all things are not equal. Theme parks are very complex systems and guests would respond in a variety of ways.
If LMA were still around, IMO most of its guests would be drawn from other tertiary attractions like Indiana Jones, Beauty and the Beast, Frozen singalong, Playhouse Disney, Muppetvision, etc. If a 2000-person average crowd at Indiana Jones becomes 1500 because some of them are pulled over to LMA, the impact is lessened.
Some guests may extend their visits longer for something like LMA, which again doesn't really have a positive impact on wait times. If an average visit of 6 hours becomes 6.5 hours because some guests add LMA to their day, it doesn't shorten the lines elsewhere. Though there could be a nominal improvement in guest satisfaction.
And let's not pretend that LMA would play host to 10,000 guests per day in 2 shows...much less 30k in 6 shows. The demand simply did not exist.
Don't get me wrong...I love to have options. If LMA still existed today, I'd go see it once every 10 years or so. (It's been at least that long since I've seen Indy, but I'm probably due.) I'm all in favor of having these tertiary experiences in the parks. But you can't just throw out any amount of capacity and assume it would have a positive effect on wait times, crowd levels or guest satisfaction. That's why "Oh, Canada" doesn't start running at 8am and why Tiki Room isn't open during extended evening hours.
At the end of the day, almost nobody paying for admission to Disney's Hollywood Studios would have the mindset of "well, lines were too long for Rise of the Resistance, Slinky and Rock N Rollercoaster, but my visit was just as satisfying thanks to Lights, Motors, Action." It's not a suitable replacement for other experiences. It does nothing to lessen demand for the "must-have" attractions, and brings little additive value to a day at the park.