River Island have struggled for ages.
They are in that odd position where the price is too high to compete with H&M, and the quality is too low for mid range middle class shoppers. (They go to Crew Clothing etc)
Who is River Islands customer? They are a 90s & early 2000s brand that hasn't adapted. COVID changing how people socialise further reduced their client base.
There are plenty of better online options where you can order hundreds of pounds of items, try them on and return what you don't want for free, or a couple of quid.
Compare that to going to a store, with limited stock and a cost to get there - whether it's parking, public transport, petrol or just grabbing a drink. Those brands only work in places like Westfield these days.
Mountain Warehouse have done a good job - focusing on bigger sized stores and now expanding their brand offerings in collaboration with Animal.