I’ve regularly sworn an oath to the Queen as a Scout, and have no problem with that – to me, the Queen/King in that context represents the country/society, I’ve never thought of it in any feudal/servile context.
Swearing an oath to the king on his coronation, for some reason seems more feudal to me without the wider Scouting context. Maybe I’m confused or hypocritical, but I’m out.
Others are free to swear an oath or not, free choice, not for me to judge.