I don't think the problem is the limitations of the puzzles they can write, but moreso the limitations they impose on themselves on the categories and puzzles they could be using. When you're offering Thing and Phrase 90% of the time as choices in the bonus round, no wonder you start to run out of ideas. Meanwhile they let On The Map, In the Kitchen, Around the House, Occupation, Show Biz, Character, and Title sit by the wayside only pulling a few of those out a season. It still doesn't feel like they've fully utilized What Are You Wearing yet.
It seems like they're sitting on a floodgate full of puzzles, both in the main game and the bonus round, that they refuse to open because it would mean expanding beyond the same six categories they use, mainly in the same structure of the show.
It's been boring to watch Headline show up only twice a year when a sports team wins a national title or Movie Title showing up only when Sony has a movie to promote. Beyond the Wheel, a lot of problems the show has could go a long way towards being solved if they'd break out of the stale rut of puzzles they've anchored themselves to for the last 15 years.