The design of K2 has not changed in the last 7 years, probably because its lead (and only real) developer quit the company to start his own somewhere around 2014 -- possibly earlier, it's been a very long time. Between then and now K2 seems to be in maintenance mode, doing the absolute minimum to keep working in newer versions of Joomla. No design or usability issues have been addressed.
I am actually surprised it's still around. Back in the Joomla! 1.5 days it had features that made sense, like nested categories, tags, comments and custom fields. All of these except comments have a much improved counterpart in the Joomla core. K2 comments are extremely susceptible to spam and even its developers weren't using them back in 2011, at the heyday of K2.
The same goes for basically all CCKs (Content Creation Kit) extensions that were popular in the Joomla 1.5 days. Their key features seemed to be custom fields, tags, category management and publishing options – all of these are now part of Joomla itself or available as third party plugins. You can even get more than decent AMP and social media card support for Joomla articles, things which are very relevant now but weren't even a thing when the CCK extensions were created.
Here at Akeeba Ltd we do as we preach. Look at our Videos category. What you see is core Joomla articles. We used core features to create a category-specific template override for the Blog Layout and some custom CSS for the articles. The static category header is a simple custom module but we could have made it with the core Custom HTML module as well – I just found it easier for maintenance to automate the header content.
You could make Admin Tools not throw a security exception. The other public tickets on the topic explained how. That would be a good short term solution. The long term solution is to identify the reasons you're using K2, find a migration path to core content and see if that makes sense for your use case. Just keep in mind that Joomla 4 – beta coming end of May in all likelihood – is likely to necessitate that transition.
Nicholas K. Dionysopoulos
Lead Developer and Director
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