as you  quote, Gospel texts do differ - ...."anyone who divorces his wife, except for sexual immorality, and marries another woman commits adultery.”

That "except for sexual immorality," seems even broader than the older translation "except for adultery". If we took that text as our norm there would be all sorts of reasons for divorce and remarriage.

Problem is that we have taken one text in one Gospel and based all our Church Rules on that, without reading all the pertinent Gospel and Epistle passages about marriage and divorce, and the passages where Jesus treats of 'people in adultery'.