As someone who is fervently anti-jira, it wouldn't be that hard to make it tolerable. Just make it so that I can't measure page loads with a wall-clock (I've clocked multi-minute loads before) that need 3-7 clicks to get where I need to be. Don't have an abundance of weird subviews that hide half the editable fields I use for another half that I don't. Make the currently active filters clear. So on and so forth, just make it usable.
I would still think jira is a bad tool (in the same way that JNCO jeans are bad pants), but at least using it wouldn't be painful.
These complaints seem like they have a couple of potential causes.
One very common load time issue is downloading too much data at once, especially on boards. I understand some work has been done to make this better, but you may get some relief by creating new boards with very limited number of issues on it - you want the board's primary filter to be specific (eg a board just for stuff assigned to you, rather than for everything asssigned to your team).
The weird subviews tend to be configurable, and Atlassian has been moving more and more towards defaults (and locking down those defaults) for these configurations that push a specific persona/way of working. I'm sure they have data that supports those choices, and there is strong selection bias going on here, but almost all the consulting I did was trying to figure out how to work around those defaults (the simple ones you can just change!)
Probably, a lot of those issues could be fixed by your administrator - you may even have permission to fix them yourself, though that process can still be quite cumbersome and labyrinthine.
So many complaints about JIRA come down to complaints about how it's configured. Atlassian knows this, and I think they are trying to make it better, but it's a hard problem. I enjoy the endless customisation available as an admin but it takes time and effort to understand what's possible, more time and effort to design those changes, and the most time and effort to make those changes match what the teams need. It's a hard problem to fix.
Sometimes people, frustrated by this big bohemoth, will pick an opinionated tool that matches their way of working. This works great for as long as that tool keeps focused and the needs of the team don't grow.
If consultants exist for a product, you know up-front that the product is intended as an "enterprise," end-all-be-all product, intended to be bought by high-level people, implemented by middle-level people, and configured to frustrate low-level people. It's not the product; it's the implementation, and it's a misalignment of incentives. Most companies big enough to afford JIRA are going to have the same kind of middle layer that winds up making people complain about JIRA on forums like this.
Mate... Jira is ~$8 a user per month. Complain about it all you like but you can't make comments about it's affordability. It's by far the cheapest option out there given it's feature set.
I wonder if self-hosting is the performance difference. I have worked in projects with 15 years of history in Jira. And they were fine. It feels kind of slow but in reality it takes maybe three seconds to load any ticket.
But actual minutes to load stuff? That is insane and I can see where the loathing would come from.
A lot of anecdotes are possibly from some years ago where self-hosting JIRA meant a single server on-premise. You might not get a lot of resources and can be used by the entire organization. The server would be at or over capacity 90% of the time so things could take forever to load.
Self-hosted JIRA also opened up to lots of customisations and hacks, which often weren't performant.
With enough data it's possible - I remember a colleague going to a conference and chatting with some Atlassian people and they said their priority (this was probably 2016 or 2017) was getting Jira to be performant for companies with 500,000+ people. With enough users, labels, releases etc I can see Jira churning on something for minutes.
I would still think jira is a bad tool (in the same way that JNCO jeans are bad pants), but at least using it wouldn't be painful.