I think that's a pretty weak excuse.
I probably don't even spend as much time gaming as many adults spend watching TV, but I never watch TV so all of that time is available for gaming. Everyone gets to choose how to spend their time, but for any adult who wishes they could spend more time gaming, breaking the TV-watching habit would be my first suggestion.
What maturity has brought for me is reduced patience for the hurdles of online multiplayer, subjecting my gaming time to the grace of random strangers and the quality of network connectivity. Therefore singleplayer content is important to me, and that's gameplay content -- context, engagement -- not just assets like a pile of cars and tracks.
Often enough for me, the climb from the bottom is the best part of a game. When you have everything, you need nothing. Making the most of limited resources or abilities is an engaging challenge, and growing or expanding upon your resources/abilities is fulfilling. I regularly replay old games -- racing or other -- to repeat that part of the experience.