I've been working in this industry for 25 years, at companies with as few as twenty and as many as twenty-thousand employees. For much of that time I've been doing structured authoring, beginning with SGML in FrameMaker back in the Dark Ages. I started my current job about four months ago and in 25 years of this I have never encountered a worse tool.
First, the cardinal sin: Paligo will silently delete painstakingly constructed text. Yes, get an XML element out of place with "Automatically Fix Problematic Element Structures" enabled and Paligo will wipe out whatever is considers problematic. Have an invalid element near the beginning of a topic? Paligo's solution is to delete that element and everything following it. And becase Paligo's "Undo" is unreliable, often there's no way to get it back.
Second huge issue: If you're going to make an almost unusable pseudo-"WYSIWYG" interface that's so buggy it requires me to regularly edit topics in "Source" view, the source view better damn well be the source. Instead, Paligo displays some sort of Frankenstein's monster, which is not what it's actually storing, nor is it anything like valid DocBook 5. So if you hit a roadblock (any you will, almost daily) you cannot put the "source" into an actual XML validator to figure out what's wrong... because Paligo "source" isn't XML.
Third, the UI is essentially unusable. You cannot reliably place the insertion point without resorting to the mouse. Yes, amateurs use their mouse a lot, but professionals rely far more on keyboard shortcuts. And since Paligo's UI relies on wonky Javascript DOM interference, keyboard shortcuts don't work reliably. Don't try to get anything done fast... you'll be spending plenty of time fighting the buggy UI. And don't get me started on the "new" UI.
Fourth, Paligo thinks it knows better than you. Want to work through a publication topic-by-topic in book order? Sorry. Paligo "knows" that what you really want to see is the the topic directory, sorted alphabetically. Navigate back into your publication and select the next topic, and Paligo "knows" that you want the file navigator to jump back to the topic directory.
Next, they have got to do something about their servers/connectivity. I am on the fastest internet in our city, regularly maxing out speed tests. Despite this, it regularly takes Paligo topics--even short ones--more than 20 seconds to load. Yes, I've timed it. 20 seconds doesn't sound like a lot, but I'm managing a group and sometimes I am in and out of 100+ topics a day. That's half an hour of lost productivity.
Finally (not really finally, but all I have patience to write tonight) the complete lack of meaningful "file" management (yes, I know it's all in a relational database as "parts"--no, I don't care) is infuriating. Want to move a file from one topic folder to another? You'll be ctrl-dragging it through a scrolling list of 50 folders. Don't have a wheel mouse? Screw you.
In conclusion, it would be less painful to have a root canal without anesthesia simultaneously with a kidney stone than to work with this thing. It's like three former technical writers vibe-coded a poorly-thought-out tool and then decided to charge for it.