Being in an unwinnable position sucks. You might as well not be playing the game.
Catch-up mechanics keep the game competitive, by giving losing players a leg-up, or holding back the winning players.
Don't specifically single out and punish people for doing well. Overt catch-up mechanics are anti-meritocratic and feelbad.
In Isle of Skye, you get income each round based on how many people you're ahead of.
Ideally, catch-up mechanics should be unnecessary, or intrinsically built into your game. If you have to add them, at least try to hide them a bit, inside other mechanics. Even if people see the inherent catch-up in the mechanic, the catch-up is not the entire purpose of the mechanic.
There are a few ways to hide catch-up mechanics inside arithmetic, with simple effects that just happen to be worse for players who have more stuff.
In my gangster game, the Showdown effect causes all opponents to lose half their health. The opponents with more health therefore lose more.
Rather than include obvious and anti-meritocratic catch-up mechanics, include ramps and big moves. These things double as catch-up mechanics.
The player only needs a chance of winning, for the game to remain enjoyable. That chance can even create tension, which is probably good.
Big Moves: In Scrabble, home players will typically score 10-25 points per turn. However, if a player uses all their tiles in one turn, for an extra 50 points, or gets a Z on the perfect spot, they can easily score 70-100+ points. If you're a long way behind, you're probably not going to win, but a big move like this is always possible.
Ramps: In the TV show Family Feud, there are three rounds. The last round is worth double points. This way, a team that has lost the two previous rounds can still win.
Politics is a very effective catch-up mechanic, but politics is often terrible in games (except games that are about politics, like many war games.) Players simply gang up on the winner.
The robber in Catan, and the Attack cards in Lords of Waterdeep, are both catch-up mechanics, as long as the players use them correctly, which means attacking the leader.
Obscuring the leader is an effective option. If players don't know exactly who's winning, they always feel like they have a chance to win. However, this should be done via hidden information. Players should not simply be able to track who's winning.
In Small World, players gain points, but then keep the points tokens face-down. Players still remember roughly how many points each player has gained. This creates an annoying memory issue, and players just argue about who really has the most points. This is bad.
In Lords of Waterdeep, each player has a hidden "Lord" card, which awards them points at the end of the game, based on some criterion. It's not just a random bonus. Some people will have tried to get lots of points from their Lord, while others won't have. It's not easy to work out who has been focusing on their Lord card objectives, so the winner is therefore obscured until the end. This is good.
Instead of having a catch-up mechanic, one option is to simply have the game end sooner. When one player would get to the point where they're guaranteed to win, make the game end.
Catch-up mechanics are internal workings of your game. If they can be removed, they should be. And, if they have to be there, they should do their thing without being noticed.