West Indies were just plain bad throughout series in batting and bowling and it cost them big time. In last game Sherfane Rutherford played decent innings of 70 runs which helped them get over 250 runs but it still was not enough against England team.
Jamie Smith really stood out for England hitting super fast 64 runs off only 28 balls. And he deserved Man of the Match reward and he showed how aggressive they can play and how easily they can chase down scores. You are right to say that West Indies bowling is huge problem. They could not even protect big scores like over 300 runs in the second match. They really need to get better at bowling if they want to stand chance in international cricket.
Not just in this series, but they are playing like this for some time now. Their key players such as Sunil Narine, Andre Russell and Kieron Pollard have retired from international duty. What is left is a bunch of inexperienced players, who struggled against the conditions in England. Keacy Carty was perhaps the only player who put up a decent performance in this series. Gudakesh Motie was good in patches, but he was inconsistent. In the long term, I don't have much hope for West Indies as a team.
Players retiring and new players replacing them is a continuous process but for the cricketing nations that are failing to generate talents through grassroot cricket or the ones not being able to connect the new players with the team for various reasons.
Every team have had highs and lows. Even Australia struggled briefly, so did New Zealand, England and South Africa but they are back to their know standard. Sri Lanka suffered for years but they too have improved at current time. Pakistan and Bangladesh too are suffering at the moment. While the problems of West Indies are unique on their own. West Indies is a loose sporting association between small nations in central America and they have their own political problems that are affecting the team, the politics is deeply rooted in selection as well between players which is leading to many players just leaving cricket for other individual or club sports. It's difficult for West Indies to get back to their intial glory and in worst case scenario, the team may disintegrate.