There isn't much doubt that the present law regarding unreasonable behaviour is unsatisfactory and, like other aspects of the divorce law, is in need of an overhaul.
In my view there is a lot to be said for a change in the law to the effect
that one year's separation + consent should suffice, as it is in some States in the USA. I think it is reasonable that there should be provision for some time for reflection. However, any government that floated the idea of such a reform would be accused of ' undermining the status of marriage ' and ' making divorce too easy ' - there was a thread on this site only this week on that very subject, with some people complaining that the law as it now stands is too easy, let alone reform !
The only thing I can suggest is that ' unreasonable behaviour ' does not necessarily mean blameworthy behaviour, the sort of thing that would make
normal people think the worse of you ; examples might be spending too much time watching telly, being a workaholic. differences over finances, and that sort of thing. If the other side does not contest it, the chances are it will go through on the nod. Which is, of course, divorce by consent in all but name Some lawyers believe it helps if allegations of UB are agreed in advance before the petition is presented.
I would have thought that irreconcilable differences could potentially be
grounds for divorce, although I guess that normally these would show in other ways. In my own case - and I hesitate to add that we are separated but not divorcing - the sticking point is that she is American and after living here has returned to America, and I want to stay here. We still love each other and want to live together, but the issue is health - both of us have serious health issues, and the USA is no place to be ill. But that seems to be something which is capable of being unreasonable behaviour, and if I did want to divorce those would be my grounds ; she is insisting that she will only live with me in the USA and both of us have medical problems which would be ruinously expensive to treat and for which we can't get insurance. Bit of a mess, eh ?
Mike