I'd like to see Symantec improve the speed of Full Scans.
Other providers such as Bitdefender and Kaspersky are MUCH quicker.
No reason Norton can't be as quick.
https://cdn.comss.net/images0002/Performance_test_2014_1.png
Probably, Norton faster on some systems, or faster on the most systems.
On the other hand - very low impact: https://assets.pcmag.com/media/images/433757-symantec-norton-security-deluxe-2017-performance-chart.jpg