All of these have pretty simple answers, to be fair:
1) Ziyech has been shite for a very long time for Chelsea and his move just fell through, why was he put straight in the team? It is the first game after most of their signings; not massively surprising that they weren't all thrown on at once.
2) What is Cucurella doing in the team? He looks like another write off waiting to happen, i.e. by the summer. Chillwell was injured; I think that youth player who he promoted is injured also. No choice here.
3) Gallagher looked quality for Crystal Palace, now back looking like a Championship player. Shouldn't be starting games. Kovacic, Kante and that other guy are injured (can't remember his name) - Jorginho is gone. No choice here.
4) £600m of signings and you still have Mason cnuting Mount in midfield. It is the first game after a lot of their signings. Same reason as the first one. Felix is also serving a ban.
5) Havertz is not a striker and shouldn't be playing as a striker. If he wants to play as a striker he can move to League One and play against shite. Who do you play then? Aubameyang is crap; the young striker they have is injured. They don't have anyone else.