Correct me if I'm we wrong, but this "all time worst" stat is referring to opponent PPG. I don't put too much stock into the "all time" or history aspect of it, simply because scoring is up so much around the league as a result of pace, rules, 3s taken etc. We're also easily averaging around the all time highs in scoring. The relative ranking for this season is what matters, and as we've seen in the example of Phoenix, you can be a bottom 5 team and still be really good if you're that much better offensively.
To be clear, I'm not arguing that we shouldn't need to get better defensively to win games. I'm saying that technically, it's too simplistic to say that the reason we're losing is because of some sort of historically bad defense (which is a point that many media members/talking heads keep simplisticallyrepeating)
I could be wrong but I thought they were going off of defensive rating and not PPG when they showed that the Kings were one of the all time worst. Here a a simple chart comparing teams from this year. Look at how many teams are all in the same vicinity and then its a big step from the Pelicans to the Blazers and then twice as big of a step from the Blazers to the Kings.
https://www.statmuse.com/nba/ask/nba-highest-team-defensive-rating-2021
Compared that to last year where they were bad but at least normal bad.
https://www.statmuse.com/nba/ask/nba-highest-team-defensive-rating-2020
I don't really worry about PPG too much because a lot of the time it's relative to pace. If you're playing faster and scoring easier, then you're using less of the clock so you're giving your opponents more opportunities to score. It's perfectly fine the way the Suns did it because their net rating was way up in the positive. It's not fine the way the Kings are doing it because their net rating is negative. The Nash Suns were never technically bottom 5 in defense, they were more mid pack when adjusted for pace and points. It only seemed like they were bottom 5 because their pace and offensive efficiency gave their opponents more opportunities to score, but it really didn't matter because Phoenix's offense had them covered.
The Blazers are a good example of that this year. 5th in offensive rating, 29th in defensive rating and 15th in net rating. They're 6th in the standings but they're lucky to be in 6th because their stats say they should be around 9th or so. They've just gotten lucky because they've won a lot of close games that could have gone either way. Without that luck, they'd be a fringe playoff team and their offense is 5th compared to our 11th place offense.