I don't agree with that, sure Guinness was not like Ewan but I think Alec was not slow or pudgy during the saber duel. He moved quite gracefully especially with the saber to Prowse, in fact if you see the BTS footage of Guinness and Prowse practicing with David in and out of the Vader suit. Alec looked pretty fit for his age and I think Lucas knew it at the time so we got to give old Ben a lot more credit.
Now Mark has really let himself go over the years. I guess when his entire career became about voice acting jobs as opposed to physical roles he probably didn't think staying in shape was necessary like Ford. He let the weight get to him, but he did say he lost weight to tackle the return of Luke, so I guess he was in worse shape a few years ago.
I'm not expecting Mark to do anything agile in this film but if he did I'm sure it would be mostly stunt doubles or CGI
Now Mark has really let himself go over the years. I guess when his entire career became about voice acting jobs as opposed to physical roles he probably didn't think staying in shape was necessary like Ford. He let the weight get to him, but he did say he lost weight to tackle the return of Luke, so I guess he was in worse shape a few years ago.
I'm not expecting Mark to do anything agile in this film but if he did I'm sure it would be mostly stunt doubles or CGI