alt Hacker NewsFFXIV's level/stat sync system is also pretty cool for keeping the older stuff playable long past its original release, players get levels and stats and skills scaled down to the max level appropriate for the content
4-player dungeons still end up being a bit of a faceroll, but it's definitely possible to wipe on the 8-player bosses if mechanics are not observed
WoW has been doing this for like a decade. A lot of the old expansion content gets level scaled for new players, many dungeon groups get scaled to the same level, some of their time travel events have scaled old dungeons up for current players, etc.