The prime of deathmatch was 1996-2000. It is now 2009 (for those of you who are a little behind). People change over time. Now people are all up into that hybrid driving epic future game with big worlds and free porn.
Its gaming evolution .
There's still a good interest in deathmatch (e.g. Quake Live, COD4, etc.) UT3 just didn't introduce much that was new. They removed a few game modes, reduced the amount of levels, had an unoriginal campaign mode, and there was little new content other than mostly cosmetic/graphical changes.
But I do agree games need to continue to evolve. Deathmatch can only be re-done so many times.
ONS was/is great in ut2k4 even thought the power node thing was/is abit silly , some maps you just charge powernodes instead of acutally fighting. UT3 more of the same powernode sillyness except there is no way to deal with certain vehicles on foot which makes it futile and depressing , TAM is a great ut2k4 mod and many were hoping this gametype would be included but it wasn't. I am however very glad that quake live has adopted TAM ( clan arena ) as its a relatively simple mod that adds flavour and excitement!