| Yes it is. It succeeded the 8th gen Wii U and 3DS, therefore it is a 9th gen console |
If people define what generation a console belongs to based on the generation of it's predecessor, all the while Nintendo keep releasing their systems more frequently than Sony or Microsoft do, we'll eventually end up in a scenario where the next Sony and Microsoft console will release after a Nintendo console, but the Sony/Microsoft console will be a generation behind despite releasing afterwards.
Something that approximately looks like this:
(2017) Switch released, succeeds 8th Gen WiiU, so is defined as 9th gen
(2023-2024) Switch 2 released, succeeds 9th gen Switch, so is defined as 10th gen
(2028 - 2030) Switch 3 released, succeeds 10th gen Switch 2, so is defined as 11th gen
(2034 - 2036) Switch 4 released, succeeds 11th gen Switch 3, so is defined as 12th gen
(2039 - 2042) Switch 5 released, succeeds 12th gen Switch 4, so is defined as 13th gen
(2020) PS5 released, succeeds 8th gen PS4, so is defined as 9th gen
(2027 - 2028) PS6 is released, succeeds 9th gen PS5, so is defined as 10th gen
(2034 - 2036) PS7 is released, succeeds 10th gen PS6, so is defined as 11th gen
(2040 - 2043) PS8 is released, succeeds 11th gen PS7, so is defined as 12th gen
tldr - Switch 5 released before PS8, Switch 5 is 13th gen, PS8 is 12th gen
To get around this issue, either the next Playstation and Xbox jump two gen instead of one, and Nintendo end up being in a generation by themselves for one gen despite having competition, or two of Nintendo's systems need to be a part of the same gen.
Alternatively you could be all like "to hell with it, screw this generation system" 
