The problem is when you want to sell.
There are a lot of people who can't see past this so won't view.
And a lot that can see past it , also know the hardworking, time and money needed to tone it down, so also won't view.
So you reduce your market.
Yes people will buy and change things, but want something they most or less move into.
Neutral colours give people a blank canvas to work on.
I used ti like house doctor where they'd get a house ready to sell
Its not a problem for someone who wants to buy a home and decorate to their taste though, as you say many people can't see past the colourful interior, others don't want to put in the hard work of changing it - thus the market is reduced and your completion for a bargain is reduced.