Because the game is older, the default textures look blurry on 1080p or 4K monitors. Community texture packs upscale the tracks, crowds, and UI. Furthermore, mods like the are essential, as they restore content that was originally paid DLC (like the Legends Pack and Speedhunters Pack) which is difficult to purchase legally today.
to your game's shortcut or Steam launch options to force the game to read the newly "unpacked" modded files. Where to Find the Files NFS Community PCGamingWiki