Not in my experience V - BBC are often so bad as to be laughable, whereas others pretty much bang on. I wonder who supplies the service & if it differs from channel to channel.
I had to laugh at Antique Roadshow last night. The expert said Foy, twice, the subtitles were 'Foy' yet it is spelt Fowey.
On the whole the BBC are no better nor worse than any other channel for subtitling but I don't watch snooker.
Live subtitles use software that recognises a word and puts the corresponding graphic up.
The problem is the software is not sufficiently savvy to recognise accents, slang words, or words which sound similar, but have different context, hence the bloopers we have to live with until it is refined, and those bugs are eliminated.
If you change the subtitle language to something like Finnish or Russian then, provided you don't speak the selected language, the lag won't be annoying.
I find the subtitles fine too except for on the news when they are always out of sync. Has the sound quality deteriorated or is it my age? Everybody seems to mumble these days.