At the time, (most?) websites didn't adjust for responsive web either. There's nothing inherent about Flash that made it impossible to support responsive layouts with it. In fact, if anything, developing with Flash gave you more control over positioning than html/css did at the time.

Sure, there were downsides to Flash. It's true that many Flash-based apps/websites used more battery power than html/css stuff. But I'd argue that this is an indicator that there is a demand for rich content on the web. Since Flash was killed, we've seen a resurgence of all kinds of heavy JavaScript libraries, and forums like hackernews are full of people complaining about websites being sluggish and slow to load because of the amount of js that's being injected. Well guess what - now we've just replaced Flash with a fragmented open landscape.

Is it better? Maybe - to a degree the openness of html/css/js is good for obvious reasons. But to be honest, I think the web still hasn't recovered from the blow Apple gave to the creative ecosystem that had been built up around Flash, because there still isn't a similar tool that allows you to easily build web-based rich, interactive experiences, full of animation and rich graphics, the way Flash did about 15-20 (!) years ago