I definitely pick Marshall in my all time XI, but I think it's fair to say that the idea of him being a consensus "locked-in" pick for such a team has become more and more prevalent in recent decades.
At or around the turn of the century, give or take, I saw all time XIs selected by Peter Baxter, Christopher Martin-Jenkins, Henry Blofeld, Bill Frindall, Jonathan Agnew, Don Bradman, Richie Benaud and Ashley Mallett, and Marshall didn't make any of them.
TMS chose their 40th anniversary team for 1957-1997 and Marshall didn't make that team either.
And if the all time rankings of John Woodcock and Nick Brownlee around that time were converted into all time XIs then Marshall misses both those teams too, and by a long way.
To repeat, I disagree with all of these, but the idea that Marshall is a near-universal lock in an all time XI certainly wasn't the case until relatively recently.