Do not panic, it is still a great series that for some reason has been maintained over time and has a large community of fans, whovians. To put you in context, Doctor Who is an alien, a Lord of Time who travels with a machine, the Tardis, for time and space helping others. The Tardis is camouflaged like the old London booths to ask the police for help.
Together with the Tardis and his traveling companions, this series offers an endless number of different worlds. In Prime Videos you have from season 5 to 10, it is a pity that you have not been able to see them all since 1963, but to enter this universe you can start with the season that you like and with patience discovering all its culture.