First of all, you may never be certain that you will get to the last boss at all, let alone beat the timer with random players. The Mythic mode requires high levels of group coordination and strategy from every member of the group. Most teams just run for the fun of it and achieving the best result with them is a dice roll.
Second, while it is fair to say that everyone can access any dungeon, there is a caveat. Mythic+ is a highly competitive community, and players have created an unofficial rating system that tells the recruiting groups exactly how skilled you are in a given dungeon.
The system is called Mythic+ Rating, previously known as RIO score, which was a a third-party website that tracked your progress in WoW Mythic Plus Dungeons. This was so popular that it got implemented in World of Warcraft.
Having such a handy way to track Mythic+ progress makes choosing the best candidate a matter of comparing numbers. It also means it’s all but impossible to find a good party after a realm transfer or for your alt. This problem is very real if you try to find a decent group on your own, but completely non-existent if you buy WoW Mythic Dungeon boosts from us.