Too much of a good thing can be a detriment to how good or special it is. Some ice cream is good and special. Twenty-five gallons not so much. The same goes for the number of Jedi that survived Order 66.
In The Original Trilogy the Jedi were all but wiped out. They were hairsbreadth away from extinction as an order. Yoda was the last surviving Jedi master with Obi-Wan being the last regular Jedi until A New Hope. And from the way they talked there were no others left alive after the implied purge by the Empire.

I remember a brief scene in the original comic book run of the Marvel Star Wars comics where I believe Han Solo and Chewbacca were on a solo adventure and they encountered what was implied to be a Jedi. But other than that near as I can recall no other Jedi were encountered in any connection to the Original Trilogy
Then the prequel films rolled around, and it certainly looked as if the majority of Jedi were wiped out when Order 66 came around. Death was all but assured for anybody wielding a lightsaber. Force sensitive people were gone from the galaxy.

And then Disney got ahold of Star Wars. Now we have Inquisitors and numerous Jedi that all survived that traumatic event. The total is something above 25 that made it beyond Order 66. An argument could be made that those in any videogames are not canonical but that is tough since there is so much ‘synergy’ these days and everything is so heavily interconnected.
Not only does it make Order 66 not that serious but implies that the Jedi were easily disillusioned and quickly gave up begging the question of how the Separatists had so much trouble with them. Yoda noted that Jedi were not of the same quality as they had once been but the inability or unwillingness of greater than 20 survivors to get back together and do what they signed up for points to an issue with recruiting standards and not anything else.

The Force allows for a level of extrasensory perception that should have told those Jedi others of their order were out there which it appears it indeed did do. Maybe not exactly where but that they existed. It looks as though no Jedi took time to look or did the very Sith thing and looked out just for their own interests rather than those of others.
Yoda and Obi -Wan seemed to have a connection/awareness with/of each other but nobody else? Of all these powerful individuals with an axe to grind against The Empire and Darth Vader or Anakin (I know they are the same person) you could not find a few who might join together themselves or just aid Luke? In a universe with evil space wizards it manages to strain credibility.

All the surviving Jedi take away from how significant Order 66 and the following Purge was. What was once a devastating event that left only two real survivors comes off more as an inconvenience and unintentionally frames the Jedi as cowards. They all went into hiding rather than attempting to regroup and do something. Not only is that cowardly but that’s selfish. And it seems to go counter to any good intentions they say they have. They were mild Sith in reality.
And it brings up the question: exactly why was Luke so necessary? How many years of training and how much more subjugation by the Sith were they willing to go through before they felt Luke was ready to take on Darth Vader? And why did they not try to recruit others at the same time? Or maybe bring in Ahsoka Tano? Why didn’t the Rebellion try since at the bare minimum Hera knew she was out there? In short two Jedi (even if one lacked experience) against two powerful Sith would’ve been a much smarter route than one impulsive boy. And that’s on top of anybody else that’s alive.

The more of something there is, the less unique it becomes and in a narrative the plot holes it can create. What is so special about Luke or Yoda or Obi-Wan anymore? Not too much. It also undermines The Empire as a threat as well as Palpatine. Adding survivors is something that does need to be dealt with. Either stop having surviving Jedi show up or do something that focuses on Order 66 to make it feel significant again. But just stop watering down the event.

