As with Koeman and the last years of Martinez, the problem is not that they are spineless - its a combination of the manager and the incomprehensible focus on 4-5-1.
Take Ashley Williams for example. Every person who has ever seen him play for Wales knows that he has to have someone, ideally two someones, next to him with a bit of pace to cover for him. When Allardyce first came here, he played someone with a bit of pace to cover for him. It works for Wales, and worked in Allardyce's first few games. Since then he has never played someone with a bit of pace next to Williams and he looks the aging grock he is.
Now if you make that mistake once, people would give a manager the benefit of the doubt. Not only has he made it more than once, he actively prefers making it to the exclusion of something that works and he makes similar decisions with regards to Martina, Schneiderlin (until recently) and a couple of other players. Footballers appear to live in a somewhat Darwinian existence where those who are good enough and in form play, and those that are not do not; we have between a quarter and a half of our outfield players who appear to be undroppable however they play (or if they are dropped, are brought straight back) which cannot provide any impetus to the people who want to take their places or the rest of the outfield players who emphatically are droppable.
What makes an already bad situation worse is the way in which our setup hasn't changed since the start of Martinez' second season, even though it has never worked and it is a style that no-one else in Europe plays. Some of our side have been asked to do this for four years now and it must be soul-destroying to see a succession of managers come in, get paid well, chat rubbish and nothing changes