I personally think the way Wesker is handled in TDC is really lackluster. Like they didn't want to go through the effort of recreating his scenes, so they gave him a voiceover in one part and just had him scribble a message in the end cutscene, lol. His appearances in CV were kinda cheesy (especially his laughter), but they they were a lot of fun. Especially since we get lines such as "sure i'm not human anymore...", and references to his organization and powers. It is Wesker's true transition into an iconic, over-arching villain.
Plus Alexia vs Wesker is the first true mutant battle we see. Although I much prefer the CVX version.
Jill isn't there because she wasn't with Chris at the time, and Chris specifically left for Rockfort to save his sister.