I think you're, and I mentioned this way back when Systematic Chaos was released, and I'm sure on average DT lyrics are better than from other groups, particularly popular groups. However I think we probably hold them to a higher standard and so we want them to be able to do better than X song.
I always find thiis expectation to be a bit much though. The amount of time they all spent honing their craft and in later years the touring/recording cycle will have left little time to devote to reading and improving as writers. They are musicians, not poets, and the two are rarely found together.
I would imagine that when they were younger the school years were fresh and they may have studied literature etc, and that was when the lyrics were "better". As the years go by the discipline fades. I used to be a good writer in my younger days but it's gone with lack of practice and regular exposure to how it should be done.
There aren't many bands I listen to where I would class the lyrics as great- Rush, Fish-era Marillion- I'm struggling for more. It's not important to me. It's all about the music and the melody.