16 of the 25 in front of him played all, or most of, their careers in the 21st century, many of them their careers parallel or significantly overlap Andy Dalton. Dalton isn't even top 10 on stats amongst his contemporaries (and he is likely to be passed by another three of his contemporaries before he retires).
Part of the reason Dalton is so high all time is he plays at a time when the game favours offence, and more games are played per season. The last 15 years average number of passing yards per game has increased by more than 30% from the 1970's, as well as number of regular season games increasing from 14 (prior to the NFL/AFL merger, NFL teams played 12 games per year) to 16 (and then 17). So not really that shocking a quarterback who has been in the NFL the last 15 years is top 25 on total stats.
Incidentally Andy Dalton ranks 14th for quarterback number of games started in the 21st century (he is also ranked top 30 all time for QB starts, although that was a Google AI ranking, so I'm not betting my life on it being correct)..