I fully agree with your point. However, I do think it's important not to let it become the tree that hides the forest.

FT seems to have an important representation of people chasing status and willing to take unnecessary trips to places that they have no interest in/reason to visit in the first place, unnecessary additional flights for the simple goal of adding more miles, or find ways of earning over 1000 avios through improbable itineraries and airline combinations as part of a trip they might or might not have taken in the absence of such reward.

I have absolutely no doubt, however, that such types of frequent flyers/behaviour represent a tiny minority of BA's GGL or indeed Gold and Silver passengers profiles. Even on FT, many of us - including you, me, and many other regulars - just travel a lot because - well, because we actually need to be in the place we are flying to. Outside of FT, this is undoubtedly overwhelmingly the case. I mean reading threads here, you could be forgiven for believing that any given OSL-LHR flight must just be full of people who have just arrived from LHR and are returning on their steps to indulge in a cheaper "ex EU" flight, but the truth is that on any given day, the CE cabin, big or small, is just full of people who are flying either to or from OSL. You could equally think that your average QR flight must be full of people just after cheap TPs, but the bottom line is that they are not, they are just mostly full of locals and long haul connecting visitors who have done their homework and found QR to offer the best convenience/price/comfort combination.

If QR does leave OW, it will be a sad day for many of us, not because of lower "TP optimisation" opportunities but just because QR is basically by far your best and often only way to find a one stop protected itinerary on OW from the vast majority of medium sized European airports to a vast array of destinations in South and South East Asia, Oceania, and Africa or vice versa. BA has a very good network in Europe, but actually a very poor network in Asia and parts of Africa, CX and MH have good networks in Asia but poor and very poor networks in Europe, so good luck trying to find a sensible and well timed one-stop itinerary on OW from MAN to Islamabad or Maputo, NCE to Jakarta or Auckland, GVA to Ho Chi Minh or Dar El Salaam, or TXL to Kolkata or Brisbane.

The bottom line is that there are no other airline in OW with that sort of coverage (and that is actually not unlike what would happen if AA left OW - a completely unrealistic hypothesis thankfully - in terms of coverage of smaller US, Mexican, and Caribbean airports but with a much lower coverage within Europe). The only one which can really compare (across the airline world) is EK. In some cases, you could of course book an EK itinerary under QF codeshares and get TP and Avios if that is what you want, but 1. if you are like me, you probably always prefer to book tickets on the airline prime rather than codeshare as it typically works a lot better in case of irrops, 2. this is still not OW, and 3. I wouldn't bet on even the possibility to accrue lasting forever. If you are on any of the itineraries above, neither the likes of BA nor the likes of CX are the solution to your problems unless you are happy to take a three flight itinerary where you can have non-OW two flight itineraries with much shorter flight times and much higher chance of things going smoothly (and frankly, I know no one flying for business who would choose the 2 stop itinerary just to be on OW in that context).

So I completely agree with you, QR leaving would undoubtedly harm some of the "status maximisers" but more importantly, it would harm many more frequent BAEC (and OW) flyers who will effectively have to take a significant part of their travel outside of OW or, if they absolutely insist on flying OW, will do so in far more inconvenient ways.