Games without an end condition aren't (usually) accepted on the site because without a proper ending, there isn't really a way to do a speedrun aside from arbitrary runs to achieve a condition. Games like that tend to wind up as LB bloat with dozens of categories for free WRs, so the site likes to have games that actually have end conditions and a properly defined Any% speedrun.
if a game is endless, you should probably set up a goal like a point amount. like tetris does. that's a theoretically endless game, so score limits are placed on runs.
Tetris isn't a good example for a few reasons, mainly because it was added before the rules we're stricter.
Placing arbitrary goals on point requirements doesn't solve the issue of too many categories - it's a perfect of example of the issue. If you create a category for 100 points, why not create 10 more categories of every 100 point increment up to 1000? Why not crate 100 categories for every point increment of 10 up to 1000? This is the main issue with point based, endless games - people who get control of these LBs often do this and now the LB is a giant mess with no logic and no good reason for the categories to exist other than "Free WRs".
Obviously not everyone would do this, but it's happened before and it will probably happen again if these types of games are allowed. Obviously if the game can be sold really well to site staff it might still be added, but it's definitely harder to get these types of game's added for this reason.
correction: Tetris puts line or level limits, though they do have a 300k point category. but yeah, point limit LBs should be kept to reasonable amounts expected for the game. 300; is chosen for Tetris because that gets you the best "rocket ship" screen.
Games that are endless are highly unlikely to be added.
There were some added in the past but since then rules have gotten stricter.
Now most games requested with goals like "get 10,000 score" or "reach level 100" are not accepted as there is no real end-goal to reach.