Thread makes no sense. How could a current Roubaix Comp w/ Di2 not allow a cyclist to 'keep up' on 'B/A' group rides?
What, precisely, are the deficiencies in any decent current road bike that would do so? Where would they come from?
An aluminum-framed, properly fitted and tuned/maintained bike w/Claris or Sora and unseized bearings wouldn't make a gnat's p__s worth of difference in such a context relative to the most expensive 'superbike'.
Silly.