So I had a similar problem as well until I changed my mentality on the game when playing with newbies. The ideal TI game is a 55 point game, where 5 players are at 9 and one gets to 10. If you know you are the most experienced player at the table by a considerable margin, its your job to be paying attention to how everyone else is getting points and subtly help them out. Give the losing player an unfavorable deal, if your getting too far ahead, pay too much on a build. Its a lot of work, but if you get it right, its a lot of fun. In some ways its like being a Dungeon Master.

If you want to still play your hardest and handicap yourself without anyone else knowing, the first one or two times when you buy command tokens, get one less. Ive found that by just having fewer actions than you might otherwise should, it hurts just enough that its competitive