You obviously have not watched much football lately.It's all down to stability of the squad though isn't it?
We conceded the most amount of goals we've ever conceded in the premier league and escaped relegation with 1 game remaining.
West Ham have been solidly midtable/top 8 for a few years with a good defensive record.
I'd be more concerned about paying £22mill on a Diop and him not fixing our issues than getting Coady in for half that price.
Everton were bad defensively last season. Mostly because of set pieces and injuries.
Wolves had a goalie that statistically was much better than all other goalkeepers in the league. Wolves' defence was terrible. Among the worst in the league. Probably worse than Everton's from open play.
When Wolves now are trying to fix their horrific defence, the first thing they did was to keep Coady away from the team. They spent big money to sign Nathan Collins, a 21 year old CD that spent last season on the Burnley bench. He wasn't a starter for a team that was relegated but has impressed this summer and will always keep Coady out of the starting eleven.
Coady might be a nice guy, I don't doubt him as a leader and it is a massive plus that he always seems to be available - but as a central defender there must be more than 100 players in the league that can do a better job than Coady.