They are damned if they use the TMO and damned if they don't.
Hypothetical question. The Bledisloe is tied one game all, in the final game we are a couple of points behind, and get over the AB line in injury time. The replay shows that a try should have been awarded, however, the Referee and ARs are unsighted and there is no TMO any more.
I will vote to keep TMOs. Maybe the technology will be improved - it usually can.
The TMO would also most likely be unsighted in these situations.
And to continue your hypothetical ponderings, at the conclusion of the game we could not declare a result. Every test match decided by less that 14 point we could have the TMO go through the whole 80 minutes and review every decision and non-decision. Ref gave an incorrect penalty for offside in the 8th minute, Wallabies kicked for touch and scored from the maul so we'll tack that try back, In the 14th minute there was a scrum awarded to the Wallabies but it should have gone to the ABs. 8 phases later the Wallabies scored so we'll take that try back to. And on and on we could go. We could then refer the game to WR (World Rugby) for an adjudication and they could decide which points stand and which don't and even award points where teams could have scored but for an incorrect decision and give 3 points for every kickable penalty goal where no penalty was awarded etc.
We might have a result within 5 days of the test (subject to appeal to the Court for Abritration in Sport). We might even have perfection, but we'd have nobody watching anymore.
Part of the appeal of sport is the instantaneous and spontaneous sequence of events - particularly the big moments in games. The highs and lows experienced by fans is what brings them back every week. Indeed talking about some of these calls can go on for years and pass into folklore. The Kiwis still talk about a no-try against Wales in 1905. Anyone who has played, coached or watched rugby for any length of time could give examples of bad calls costing them a match. Life's like that.
I've never met anyone who stopped watching sport because a dud decision went against them. I can give you the names of a few who've stopped watching because it's boring.
EDIT: And I'd also point out I'm in favour of the TMO being used to adjudicate the actual act of scoring a try as was originally envisaged - and this would mean that your hypothetical scenario would be covered (assuming that the TMO could see anything). I don't think that anybody has suggested taking the TMO out of this type of situation.