Ignorance is bliss.....
Yawn...explain to the non-pilots again....
A tis old chap, the expert decision on diversion combines fuel remaining, weather at alternate (and 1/2 others), landing distance/performance on available r/w's, notams, tech status of aircraft, ground handling and expected speed of turn-round, repatriation of inbound pax from diversion to destination, engineering support at alternate, number of other diversions heading to alternates, , effect of diversion options on FTL's, and feedback even from CC on the state of play with sick pax.
We don't pick a diversion field at the end of a long-haul flight because someone on prune doesn't like Manchester. But experience of the place's awkwardness in accepting diversions comes into play when quick decisions aloft are needed. As a passenger, why don't you wind your neck in? You don't understand the issues. Stick at being SLF.
MAN is not a competent international airfield in many ways, as agreed by many who operate into many fields in the UK and overseas.I would look quickly at EGNX or EGSS coming off a long-haul, maybe EGBB. If I had a choice that is...and if not, then MAN we're coming in. (Mayday if necessary).