This becomes a huge problem when someone is linking you multiple tickets and you sit there waiting for asana to load. Even worse, I find that some basic features are still lacking such as the ability to strikethrough text.
(yes, there are some command line tools that people have written, but they're too limited, for this reason, unless something's changed in the last ~6 months since I last looked at them)
And as for the backend, I wouldn't call it dumb, exactly, but it was implemented in a way that would help spur early growth of the company - and it succeeded in doing that, so it wasn't a poor decision from that point of view. We really, really do know that we've outgrown it now, and are hard at work replacing it with something better. That happens at just about every company as it scales. The frontend is constantly getting faster as we adopt the rewrite, and the faster backend for the API has just entered open beta, as a matter of fact; you're welcome to try it: https://asa.na/fast-api.
Glancing at the docs, it looks like they've gotten better in the last few months, which is great. Maybe some of that stuff's been fixed. I'll take another look at it when I've got some time.
More broadly, there are three things that would remove nearly all my complaints about Asana:
1) Clicking on a link to a task from outside Asana should bring up an ultra-light view of just that task (and its comments and such) that loads in under 200ms—under 100ms, ideally. If it must be read-only for this to happen, that's OK. Provide a link to open it in the full "app".
2) A light (think: basic-html-mode Gmail) version of the app itself. Most of the dynamic features are liabilities for me. Drag-and-drop happens accidentally more often than intentionally. Sometimes all the JS steps on its own tail and makes my cursor, and my typing, go places I don't want it (happened this week again, actually), along with other periodic, odd glitches. Editing task titles and such in-place happens more often by accident than on purpose. Every time I mess around in Asana I leave not certain whether I've mucked up the project without noticing. I'd much, much, much rather have a very fast-loading low-memory interface where such things happened only when I wanted them to. I don't mind full page loads if necessary (see again: basic html Gmail, which is faster than regular Gmail and certainly Inbox, most of the time, despite frequent full-page loads). I'd be happier with a zero-javascript interface, really, since the JS features mostly get in the way. However, with how much logic I suspect is housed in the frontend to achieve what's seen in the "app", this may be asking a lot.
3) Search. It needs to do The Right Thing by default. It should search the project I'm currently in unless I tell it otherwise. It should support inline filters, with auto-suggestions (as in Slack's search) so I don't have to clicky-clicky-typey-clicky-typey-clicky-typey-clicky to accomplish even fairly simple searches.
4) (BONUS POINTS!) Slack-style @ referencing, so I can just type it and don't have to use the autocomplete list to make it take (rather than just adding the text literally and not referencing the person I was trying to, which is what happens now if I don't select someone from the autocomplete list)
5) (BONUS POINTS 2!) It'd be nice if the "Inbox" displayed something like a colored diff-view of each item when it's selected, to make it easier to see what's actually changed. Clearing my Asana inbox takes more time than it ought to.
6) (BONUS POINTS 3!) Add an option to reverse-sort and never collapse any part of comments sections on tasks.