How to fix the Las Vegas Raiders?

It’s impossible. The Raiders suck, Gruden sucks, Carr sucks, the city of Vegas sucks. Almost as sucky as NYJ

The defense needs to be significantly upgraded.

This is not a travel question - you posted in travel/United States/Las Vegas.  You will get better answers if you post in the right spot.  In this case Sports/American Football.

To answer your question:  

1. Ownership needs to be dedicated to winning.

2. To be a consistent playoff / winning team you need to have the right combination of coach and quarterback.  

2a. It's possible to be a one year wonder in the NFL with a great defense, but to be a perennial contender you need a great quarterback who's skills mesh well with the coaching philosophy and said quarterback needs to stay healthy.  Examples - The 49ers in the 80s, Cowboys and Broncos in the 90s, NE Patriots from 2001 until 2019, the KC Chiefs from 2020 to ...?   

3. Finding that quarterback/coach combination is very difficult.  

The Raiders had their dynasty period back in the 1960s and 1970s.   

pro sports are scripted from players Birth to high school to college to draft to superbowl to careers.

LA raiders isn't a team its a corporation.

Study Gematria.