The FTSE is where it was 17 years ago. Since this time everything has gotten way more expensive.
Anyone in the UK following this advice from age 20 to 35 is staring down the barrel of working forever.
The problem is they have a share in growth in the UK over the past 15 years and that growth is next to nothing.
IMHO the old advice needs to be taken with caution. This is not your dad's market.