I'd describe mild as a lack of drastic change in temperature year around. We normally get temperatures between 0C and 20C, with a few outlier days (more so recently - lots of heat waves for obvious reasons...) This changes from North to South, but we rarely get temperatures and crazy weather like you guys in Europe have at the moment.
I'm not from Europe, I'm from India. Other than that, got your points, thanks. That frequent drizzle or rain and also somewhat frequently varying weather I've read about (mainly in kids' stories and later novels with England as the base location), make the UK weather sound interesting. I've lived in places like that, and also in others, where there are well-defined seasons such as wet and dry, hot and cold. I like both kinds.