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.