Correction, the Relic Weapon is NOT by any means, a catch up weapon, a catch up weapon/gear are items that have the easiest and fastest form of access to, so that players that are fairly new to the game and are behind/trying to catch up to the current endgame minimum ILs, can equip their fresh recently level cap job to the IL that can allow them to access and progress any content and every main content of the game (i.e. MSQ), once the player finished the MSQ, there's no more catching up to do, they are on endgame. A weapon that needs any sort of grind/hours put into getting it to finish the story its NOT a catch up item.
The Relic is although an alternative to players that don't want to engage in midcore/hardcore contents (extremes and savages) to get the best possible status after the respective work (be it tomestone grind or something else) they can achieve by other means, they should be achievements, just as much as clears and savage BIS are for players that put time and effort into clearing the hardest contents in the game.
You can still clear everything else in the game with a tome weapon, or a crafted one with the upgrade, and whenever the patches allow people to acquire upgrades in other forms (hunts and alliance raids) you can get that tome weapon upgraded, which then, serves as the catchup weapon for the players late into endgame (and to be able to do extremes and savages you can prog/clear these using crafted sets, so idk what is your point).
Edit: The only thing required by the game from the player that wants to engage in hardcore contents, is the min. IL, which is easily reached with a crafted set in the case of extremes and savage. For ultimates, well, they still need to clear the tier of the ultimate they want to do, thus acquiring gear sets and items to prepare for the ultimate in question, at this point in time, most BiS pieces to tackle an ultimate are from dungeons anyways, this last step of the relic isnt even the optimal weapon anymore because of the way the status distribuition is made.
So my question to you is: If you believe a relic is a catch up weapon, what endgame content does the game have that the player can't access unless they have a relic in hand? If the answer is "none" its because there's simply no catching up the relic offers (and if you say savage/ultimate then you are objectively wrong, since they are not required to enter/clear said content).