The FA Cup has lost most of its glory. All big clubs field B teams in the cup because they want to rest players they need for the EPL and Europe. Clearly shows most big clubs don't care about the cup anymore and prefer to focus on the league and Europe. A trend happening in many countries, while for small clubs the cup is still something special the big ones don't really care anymore. Happens in many European countries, although they will rarely admit it. But the number of big teams fielding reserve players in their national cup says enough. I think the cup is the least priority for most clubs nowadays.
The problem with the FA Cup is that in England, the league is much more lucrative, whether you're at the bottom, trying to stay in the Premier League (worth 40m a season), or at the top end, where this season a good 8 sides had Champions' League ambitions. The FA Cup is prestigious, but not lucrative. Why bother trying to win it and sabotage one's league success for a UEFA Cup slot, when you can concentrate on fourth position which is more valuable than actually winning a trophy? The Champions League and Sky's TV money have ruined the FA Cup.