Barring serious illness/disability yes it's ignorant and rude
I aim to be somewhere 10-15 mins "early" as generally speaking that then builds in time for any last minute "emergencies", if I'm going somewhere I haven't been before I'll check travel time online and if it's not too far do a "recce" eg for a job interview I'll do a dry run, at the time I'll be travelling (cos traffic flow and public transport timings vary especially in rush hour), check what parking is like etc. If it's somewhere far I'll take the average travel time and allow an extra 25%
I've had friends and work colleagues who've been pretty bad for lateness.
I've been a "boss" at times and I'll willingly admit if someone is late for a job interview I was far less inclined to hire them, especially if references alluded to timekeeping/reliability issues.
The worst experience on this score though was when I went for a job and the INTERVIEWER was 2 hours late! And they were on the premises, no emergency just a dick! I was young or I'd have walked, the interview was poorly conducted too but I was too lacking in confidence to say anything at the time. I didn't take the job though I knew the person that did - they very quickly regretted doing so and left. High staff turnover at this place understandably so.
But by far the worst for me are my mother and sister!
My sister I am now nc with. Not because of this but it was one of the lesser (in the grand scheme) of her faults as to why. Never just a few mins late repeatedly several hours!
She has had social services involvement and lost jobs as a result of her attitude to life in general and to being on time in particular. Social services as she was repeatedly 2-3 hours late getting kids to school, if she was going to be even later than this she'd call them in sick even though they weren't sick.
Jobs she would be on time for interviews, and on time to start work for the first few weeks or even a few months, then the more comfortable she got, the later she'd be each day, full of excuses and then eventually she'd be sacked...but it was NEVER her fault, nothing ever is everything is always someone else's fault!
My mum isn't quite as bad as my sister but I manage her by telling her the time she needs to be somewhere is 60-90 mins earlier than the true time and several relatives have since copied me and that seems to get her there roughly on time. She underestimates how long a task will take or how long a journey will take.
She's absolutely adamant a particular journey she takes a few times a week "takes 10 minutes on the dual carriageway" when it in fact takes about 20 once actually on the carriageway and she doesn't account for the time it takes her to...get her coat and shoes on, find her bag, fetch her keys/phone/purse into the bag, lock the door, get into car, drive to carriageway, drive from carriageway to where she parks...
And that's IF she doesn't at the last minute decide to wash the dishes or put a load of laundry on the line or whatever 🙄
It's maddening but she's in her mid 70's she isn't going to change now!
Certainly anyone I've dated or been at start of a friendship with and they're perpetually late I'm not interested in developing that relationship.
As I've got older I've stopped even waiting about for such people. I'll wait 20 mins unless I'm eating a meal and then I'll wait 20 mins before ordering, doesn't bother me eating out alone. If I'm not eating and it's a meet and go type thing then I go on with my day.
Very rare they get arsey with me as they know they were late and it was their own fault.
I find it particularly rude especially in this day and age if they also don't contact you to tell you they're going to be late. It's so easy to do these days and let's be honest if you are meant to be meeting someone 20 mins away and 20 mins before the meeting time you're still faffing at home you KNOW you're going to be late so let people know.
I have one of the conditions mentioned as an acceptable "excuse" ocd, I also have a physical disability that means I can no longer move very fast and can come across issues of accessibility - I plan and account for these. Not hard.