For reasons many fold no doubt, BOH has always, and likely will continue to be mainly a package holiday airport.
Scheduled and lo-co services trying out new destinations have come, gone and went, fact is really only flights to the C.I's stay the course, and even that traffic is mainly seasonal.
BOH is bucket & spade and long may it continue - SOU has nothing to fear.
OTOH prior to Flybe going and Covid-19 arriving ---
SOU and EXT both did see decent regional connectivity, with business traffic too.
Plus we did have long haul connections possible with DUB, CDG and AMS (although KLM ditched their SOU-AMS not that long ago)
As for the future of SOU ?
Well.....What to do?
Come back here in 12 months time for a re-think.
PS I'm in Dorset too!