No. ilvl sync does not restrict your level, nor does it in any way restrict you to lower level content. What it does is restore game balance by preventing excessive overgearing of content.
Great. thank you for that. So, if what you say is true, why would a more effective ilvl sync have any more impact tha the disinterest of players such as yourself already has? If you and those who think like you are already avoiding such content, what does it matter to you if there is a more effective level sync?
I'm going to presume then that you never participate in any FATE below your level? As for tomes not being an incentive. I'm sure that it must be great not to need/want any more tomes, once again though, it underlines the point that the content we are discussing is not very relevant to you already, applying a more effective ilvl sync would not in any way alter your calculation of whether it's worth participating in it, and nor would it alter that for any other players like you - since you don't do that content anyway, and you don't want/need the tomes.
Fatigue among high level veteran players at end-game? Sure, that's not a new issue, it's always going to be an issue. Here is an alternate viewpoint though. I've watched this same thing play out where veteran players burned themselves out on lower level content and became so overpowered that the low level content provided no challenge. The result was a large group of high level players bored to tears running lower level dungeons because they could ignore everything, one shot trash and melt the boss. The overpowering of content by both level and gear ultimately meant that those players got pissed off whenever any new/low level player asked to run some lower level dungeon, or they'd run it, and the new player would get pissed off because they got dragged through the dungeon without any input and were both bored and alienated from the game.
Oh, and just so you know, there were some dungeons with two or even three levels of difficulty, the low level version might (for instance) be level 30, and the high level one might be level 50. The high level players were far, far more apt to run the harder version than the lower one because there was zero challenge in the lower one. To me, that is an absolute demonstration that for the same content if the degree of difficulty is preserved to some extent, people are more likely, not less likely, to play it.
The level sync in the pre-50 dungeons is one of the best things that SE has done with the game because it preserves some degree of the original dungeon.
Except that the relic weapon quest was expressly designed to be a long grind as an alternative for players who were not running coil, or extreme primals, allowing those players a path to upgrade, simply by playing over time. It was not designed to be rushed by speedrunning certain content into oblivion, that is unfortunately how many people play it. It makes me wonder though, if these players already have the raid level gear, why are they bothering with the relics? Given their gear, those are optional to them. In which case, they can hardly bitch about having to re-run content for items that are in terms of their gear are side grades. Again, the relic quest line was designed to be a long term grind. If anything, the players speed running and grinding it into oblivion are making it harder for everyone else because the acquisition rate of upgraded relics forces SE to make each stage extremely grindy to slow the players down. Thanks for that by the way.
This actually argues against your stance. The point of the relic quest line was to be an alternative to the raid and EX mode weapons for players who were NOT (for whatever reason) running coil or EX primals. It is specifically designed as a way of allowing people who just play the regular content to have an upgrade path for their gear. The people who will move on to the other gear will move on to it anyway, the people who the relic upgrade quests were designed for will continue plugging away at the game and upgrade their stuff in due time.
Love the doom laden comment, you sound so much like a soothsayer of old. Doom and gloom aside, I believe that* you are very wrong. In my opinion*, you've missed the point that there are 3 avenues of gear acquisition in the game. What you suggest does little more than funnel everyone into one of two alternate ways of getting gear, and a large portion of the player base has already demonstrated that they do not want to go either of those paths. Kindly leave the third path alone.
* - added to make it crystal clear that I am stating my opinion that your arguments are wrong.