Any newer aircraft reflects the advances you see in newer consumer electronics: if you’re on a 787 or A350 the screens are large, colorful, highly responsive, with a much larger selection of content, and none of the ugly control boxes taking up space because the screens are basically modern fast and slim Android tablets.
Seats are purchased by the airlines, they are made by separate manufacturers like Recaro or Zodiac and not by the airframe manufacturer (Airbus or Boeing). While the seats obviously need to be compatible with the airframe, there are a wide variety of options and it is common for airlines to refresh old airframes with new seats.
IFE systems are not manufactured by the airframe or the seat manufacturers, they are made by companies like Panasonic. They obviously need to be compatible with the seat, and my understanding is that it is uncommon for airlines to update the IFE system without also replacing seats.
So, while a newer aircraft type typically will have a more up to date IFE system, there are plenty of old aircraft that have new IFE and seats retrofitted.
They need to do this to remain competitive in the premium cabin market.
i.e. those brackets exist and are available on many airlines today. Sometimes they provide wifi with the ability to connect to the provided entertainment system (so one doesn't have to bring one's own content, just the display device).
Also, in Bluey in Australia they say "Cheese & Jam" or "Biscuits" or whatnot instead of any swearing and it's always as a sound of frustration at the environment. Is that censored in the US version?