I consider myself quite the expert on building better organizational cultures in tech companies. You can fix process, level up people, build team work, set and communication better strategies and alignment across the work.
What you can't fix are shitty leaders. Most of the time, people build walls to work around them. Over time, the teams get worse because silos form to protect decent teams.
You can't have an effective team without trust. You can't build a healthy org culture when your leader is toxic.