I mean you could handicap yourself but it is pretty bad on peoples self esteem if they loose to a handicapped player.
To me, it was more disheartening or even downright aggravating how good players would play out their entire decks with Village + Smithy like combos, while the rest of players waited 20 seconds to 4 minutes per
each of those turns. One of the main "sells" of the game where game flow goes quickly is now nullified. Hearing that THAT player ended up doubling your score... the damage may already have been done.
As for the OP's Q:1) A better way would be to let others know what you're doing ahead of time so they could either better match or beat your strategy
2) Simply refrain from doing stuff like playing out your entire deck. Limit it to drawing up to 10 cards per turn.
3) Make "special Landmarks" that only affect you...
-Vs. each other player, you must win by at least 5 to 15pts
-grab a Chess timer, or use an app on your phone, and limit the time taken per turn, or for the whole game... probably no more than 20s per turn? Not counting Cleanup, as you can do that while the next player starts his turn
4) let players get away with murder
Figuratively. One game, a newbie got excited b/c he played a Moat, and drew in a 2nd Treasure Map! However, I pointed out that he had no actions left to play. He was disappointed. He let it be, and insisted upon so. I would've been willing to let him go through with that anyways
5) Go first, but let other players have one extra turn.
This tends to trip up new players. If you run out of Provinces and Victory cards, let them buy "virtual cards" or proxies. No matter how many they buy, game ends with the player to the right of you. As mentioned below, I don't think newbies can utilize first turn advantage unless you coach them
Go last.
This alone may not be enough. Newbies probably won't understand the game enough to be able to properly take advantage of it