For instance, I have collaborated with people using Skype, Discord, WebEx, Slack, IRC, Facebook Messenger, Microsoft Lync, icq, AOL Instant Messenger, Paltalk, Tivejo, Go To Meeting, etc.
People will tell you horror stories about all of those things, but I have found them all to be adequate. Often people conflate problems with their audio and network with problems in the tools. It also seems that these tools have made little technical progress over the years, I mean, Facebook Messenger doesn't seem very different from AOL Instant Messenger.
Having them all installed at once is a problem though because most of them want to live in the tray and will cause slowdowns and distractions while logging in. Today many of them are written with Electron and other cross-platform toolkits that many think are bloated for apps they use all the time, but it is insane to have five of them running in the tray.
Same is true for other kinds of collaboration tools, say case management/issue tracking. For instance, a customer of my customer submits a trouble ticket to my customer, I have my own ticket system (so I have visibility into my workload, history, etc.) and then I find the problem is because of one of my suppliers, so I have to make a ticket in their system. At least one of those systems is going to have a system with a login procedure like
https://www.bing.com/videos/search?q=get+smart+intro&view=de...
and take 45 seconds to load the page for creating a ticket.
At some point people give up on having it work right and just accept the problems. If you want to be a world-class remote, you can't do that.
As far as issue tracking, unfortunately I think the functionality and workflow differs too much between products for there to be one UI to rule them all.
There is actually one collaboration tool that has been able to work somewhat well (not without cons) across all UI implementations: email. That might be something to think about.
I don't think that a tool unifying all these apps is desirable nor even possible right now (because most of the protocols used are closed anyway): You'd either end up with an atrocity that tries to accommodate each feature of each of these apps or you'd have to settle for the lowest common denominator, which probably is just video, screensharing and chat. The latter might not be the worst outcome. In fact, an app that does just that could provide a superior user experience.
This begs the question though why this isn't possible with existing solutions already. Why do collaboration tool providers seem to be motivated to make their products ever more complicated or sometimes even worse than the previous version? Feature creep is a part of that problem but often collaboration tools are only seen as a small component of a more comprehensive ecosystem, as exemplified by the Skype / Skype for Business / Lync trainwreck. Skype was (and still is for the most part) an at least adequate solution. Then Microsoft bought them, intentionally made the product worse in some respects while rebranding their less-than-adequate solution Lync as Skype for Business in order to push their other enterprise products.
Why is there - as you rightly said - no common standard like email that works across all UI implementations? I think the answer to that question predominantly lies with the fact that we still have too little remote collaboration, particularly in-between organisations. As soon as remote collaboration becomes more widespread - which it inevitably will - the default even rather than the outlier we'll sooner or later have to agree on common standards just as we had to with technologies like the phone or electric power distribution.
Organizations will have to decentralise in order to continue to be able to compete, grow and scale. Larger organisations, which for the most part already are distributed, will have to become even more distributed to keep up.
The big differentiator in my opinion however will be the individual's ability to work from anywhere. Not only do companies around the world spend ridiculous amounts of money on keeping everyone in the same office, there to pretend to be 'working', but nobody also seems to be willing to actually talk about the elephant in the room when it comes to environmental issues and keeping our cities from collapsing: Commuting.
Doing away with the need to commute could be a large contributing factor to fighting global warming. Yet we as a society are mostly ignoring this while at the same time seriously talking about abusing automated driving to allow people to commute even more.
It's only 4 MB and handles tens of thousands of Slack messages in one chat without lag.
Not 100% sure what the next stage is, though. I personally find e-mail a pretty good medium for having a considered discussion -- but it doesn't seem to work that way for everyone. Maybe an opportunity there?