I don't disagree that Atlassian programs are generally bloated, but it is interesting to see everyone jumping at JIRA when its Confluence with the CVE...
JIRA is too many things to too many people - in the quest to be everyone's bug tracker, they wrote (badly) in the whole kitchen sink. This is a general issue with most software, though. Especially big software.
You cannot have complex capable software that is also simple. That's an oxymoron. You can have complex software which works, but it is difficult to get there, and keep it there. There is simply too much that can go wrong that over time, it almost must go wrong.
Keeping everything 'simple' is not an alternative - the world is complex and so even a bunch of simple things, when put together, make something complex. Think unix shell scripts which can be so much sphagetti. The unix philosophy is to keep things simple, and yet ignoring the complexity leads to its own complexity.
That's the real 'terrible engineeing practices' which get down Atlassian and everyone else's programs.
Someone said 'use paper' or 'quit and become a llamma herder' - these seem simple but again, paper burns, shepherds get shot or held up by drug gangs.
All to say, I don't think JIRA is actually that bad. There could be worse products, there could be better. But it would exceedingly difficult to make something simple which also served everybody.