I find the idea that kondo is extreme or too sterile odd, it’s not about getting rid of stuff, it’s about choosing items in your life that bring you joy (however you interpret that!) and respecting/looking after them.
Anyway, OP you said you’ve purged belongings but still the house is full and gets messy easily - so it’s a storage/organisation problem?
Which areas get messy first? I find that clutter attracts clutter. For example, there’s an end of my kitchen worktop where I set my ‘command station’ - a file for current paperwork, to do lists, diary, magnetic whiteboard etc - but because it was stuff on a countertop, it attracted more stuff because it was easy to dump a few things there without it looking too different, and before long there’s a heap of papers/change/receipts/the dogs medicine/letters I meant to post/random toiletries I emptied out of my handbag and it’s a mess.
I strip it down and keep everything possible ‘away’ either in drawers or in baskets/boxes/containers etc so even if they are out on display random clutter can’t join them. Having a place where everything lives is the key.
I’m a little addicted to organising videos on YouTube. There’s tonnes. I’ve stolen loads of good ideas from there.