The main issues with previous BCIs were that the electrodes were larger, less flexible, and not as biocompatible. This caused scar tissue to form around the electrodes, degrading the quality of the signals and eventually making the device useless. Neuralink has apparently reduced scar tissue formation enough that the implant receives usable signals for years. Neuralink also uses far more electrodes, improving signal quality and adding redundancy. The number of electrodes necessitates the use of a robot to place them. The robot is programmed to avoid blood vessels, which also reduces bleeding and scarring.

It will be quite a while before we know if they've managed to mitigate the issues enough to last a lifetime (and support upgrades), but it's better than previous devices.