Why this change? Google says it is to “improve user experience.” But how does this improve your experience?
The target use case for this change is campaigns that are time-sensitive, such as campaigns that will only run for a few days. In most cases, you will set those up in advance but leave them paused so that you can click “go” at just the right time and have the ads show up as soon as possible. Before now, though, it was possible that one or more of your ads might get stuck in “under review” status (where the ad does not show until Google reviews and approves it) and then not be approved (or worse, disapproved) until it was too late for your time-sensitive campaign.
Now you can (and should) create your ads for such campaigns ahead of time with confidence that your ads will be good to go when the crucial launch date arrives. If a paused ad gets disapproved, you can correct the problem and resubmit it just as you do now with running ads.