It's kinda weird to single out Samsung here, because they are pretty good with security updates and they explicitly talk about long security periods in their marketing. They are not as fast as Pixel, but somewhere mid-range and up (A5x) get monthly updates and they are usually 1-4 weeks behind Google.

It's the other vendors that are the issue. Even Fairphone is behind a lot (and they only release one model at a time).

The "(and others)" part was about including the other OEMs :-). I used the Samsung flagship as a specific example because it is very expensive, and people who buy it don't have the excuse of the price.