A reasonable concern and one that I am very willing to tolerate. I have no disagreement with anything you said. Most of the stuff I typed out was just in response to queries as to why an LFD system would form groups faster.I don't think anybody disagrees that a group finder would make putting groups together faster. Given that GW2 allows not only cross-world, but also cross-region grouping, queues would be near instant (all you'd need when you don't have specific roles to fill is five players being in the queue, anywhere in the world). But it's not a free lunch.
The problem is that this convenience comes at a price and that group finders have adverse effects. They tend to destroy server communities; LFD groups tend to suffer the usual problems of anonymity on the internet (warning, NSFW language behind the link); just because it's faster to form a group does not mean that you won't pay for that by finishing more slowly (see: Jin'do the PUG killer above); and content gets nerfed to eliminate individual responsibility. There are those of us who do not think the costs are worth the convenience.
I have not done a roleless MMO (does RO count?) but I have had many problems just trying to recruit and retain simple dps roles in BC/WOTLK before LFD. My WOW raid life prior to LFR is limited to how far I can drag a group of no GS, no addon, no vent, assumed underequipped or at least within 2 tiers of current content before leavers completely defeat the raid. The only wall I ever saw to hinder me was logistics. And no we never full cleared. It would not be realistic to expect a single run to be able to anyway since I don't ask for overgeared allies. It is only realistic to expect 1-2hr max before people start to leave and an undergeared raid will rarely breach saurfang/purticide (depending on raid strength and possible wipes) on ICC in the time.
Cata launch per nerf 5man heroics was no wall to progression for me and neither was Jin'do. With a full team I cleared them frequently, often pulling 3 heroics an hour at the peak of my activity thanks to a tank's instant queue. As the leader of the PUG, I find runs go smooth as silk if I help out. If there's an interrupt that needs to be done, I give the party advance notice and remind them again during the pull (with avenging shield and hammer(now rebuke) I often do it myself whenever possible). If there's a cc that needs to be done, I mark out and help them find the ability on their action bar if need be. If there's an incoming dmg spike, I pop CDs and warn the healer in advance. If there are mechanics, I give a quick 30s explanation and continue to remind the team during the fight what needs to be done. Where possible I assume I will need to interrupt myself and my entire team will be undergeared and need assistance. I retain a 99% success rate on WOW LFD during the difficult periods. The only fails come from unsalvagable parties that are intent on trolling. (total of 4 lifetime fails since LFD started). In such cases, we part ways but it is truly a minority. Sample size in the hundreds.
I have nothing against people who dislike LFD/LFR or automation and prefer manual recruitment and guild only runs, even when they can do this in the presence of an automation system. We all have our preferences. I personally find automated random groups fun because it generates a new set of allies to run with all the time and getting to know them can be socially enjoyable. I admit I am probably biased since the other options to me are limited (no guild runs and have past trauma with spamming for allies).
It is GW2's decision to remove the LFD and you will not hear me disagree with what they want to do even if I don't like it. That said, I will keep an eye on GW2 to see if coop is easily found or if they have a change in direction to include automated LFD in the future.