Email signoffs are HARRRRD. I use "best regards" or "all the best" as "yours" feels too formal.
I work with young people (mostly) in a university and it's clear some of them haven't been taught or learned how to do basic polite emails (or any kind of correspondence with an organisation to get a thing done).
Some students are barely literate in emails, 1 liners, 3 words. No hello/goodbye. I can understand why some academic staff get very narky cos the students don't have email-etiquette at all and can do things like start sending chaser emails after 20 minutes, demanding replies to 2am or Sunday night emails in minutes, or just make demands with no please/thx or salutations.
I actually think the uni should teach email-etiquette and get students to think about who they are writing to, how they wish to be perceived, what is and is not polite and where those 'ranges' might be, and what clues they can find to identify what is/isn't polite.
I started in the workplace where computers and emails were still newish and as someone with mid-90s Internet/netiquette skills, I looked at people's emails carefully to identify cultural norms, what is/isn't polite etc. I make a point of being more polite than not, especially if I am emailing someone I don't know. I don't think that's a skill that is passed on to some people these days either.