When Scott Gimble came onboard as the show runner, he absolutely ruined TWD. Since he was promoted and no longer runs the show on a day to day basis, it’s gotten a little better but too little too late. The only 2 characters I really like now are Negan and Judith (especially when they are in scenes together).
As far as FTWD is concerned, I watched part of the first season and quickly realized that I wanted every one of the main characters to be eaten or die some other agonizing death (the most unlikable casts of characters I’ve ever seen on any scripted TV series).
Most TV shows exhaust their premise after five to seven years and become stale and repetitive. The culture also tends to move on to new issues and concerns. TWD has had a good run but seems unlikely to be able to continue based on Daryl and Carol in spite of the strength of those characters and actors.