Jesus said divorce is permissible in the case of marital infidelity. Jesus’ word trumps Church Doctrine.
You need to read Mark 10 very carefully before simplifying the word of Christ in the manner you stated. First of all, Jesus did NOT say that divorce was permissible in the case of marital ‘infidelity’....infidelity is a word that has much broader meaning than just adultery and it essentially means ‘lack of fidelity’ (anything less than total loyalty to a purpose). As such, the word infidelity not only includes the act of adultery but it also includes the case where one of the spouse refuses to have sex with his//her lawfully wedded husband/wife. Furthermore, what Christ actually did say was that divorce was made permissible under Jewish law because of the ‘hardness of their hearts’.....this was recognition of the fact that some people just simply would not forgive a spouse whether this was for the act of adultery OR the withholding of sex from his/her lawfully wedded spouse. Forgiveness and reconciliation was the preferred path even in Old Testament days.... but divorce was allowed for the case of adultery (albeit against the will of God).
Finally, it is very interesting to do a word search on every time that Christ used the word adultery. It shows up 13 times in the New Testament......4 times to say ‘don’t commit adultery’, one time when he clarified that adultery also included not only the physical act but even forming the mental image of the act..... and the point I want to make, 8 of those 13 times were various ways of saying that if a person remarries after a divorce, they were committing adultery.