Thing is, the home World Cup in 2019 was a huge priority for the England. Strauss as director of cricket basically made ODIs the most important format for the team in the 4 year lead up. We played loads of ODIs, the ODI team got less rotation and resting than the Test team did, they had a core group who had played together lots and had gotten into the habit of winning games and series together.
After 2019, the ECB flicked the ODI switch back to "off". Obviously COVID happened, but even in other years we just haven't played many ODIs. And when we have, it's the format that's seen most rotation with Tests (rightly) but also T20s prioritised. Not only that, but the domestic 50 over comp has been sidelined - it runs alongside the Hundred and thus features mostly reserve players who can't get a franchise gig.
So we don't really have a settled team, and they've barely played the format even at domestic level in years. (Plus away conditions, aging team, no Morgan captain, Stokes can't bowl...)
Eh, we've got some good players so we've got a shot but we're not well prepared for it.