They're definitely not competing directly if that's what you mean; the sales show that. If they were the arrival and massive success of the Switch would've cut into PS4's sales, but that didn't happen. There's a lot of overlap between the two as well, with millions of people owning both.

The arrival of the Genesis launched around the peak of NES sales in the US.  It didn't cut into NES sales, and their was a lot of overlap between the two with millions owning both.  The Genesis did not compete with the NES.  The SNES on the other hand....

The arrival of the PS1 launched while the SNES was still selling strong.  It didn't cut into SNES sales and there was a lot of overlap between the two with millions owning both.  The PS1 did not compete with the SNES.  The N64 on the other hand....

The arrival of the XBox360 launched while the PS2 was still selling strong.  It didn't cut into PS2 sales and there was a lot of overlap between the two with millions owning both.  The XBox360 did not compete with the PS2.  The PS3 on the other hand....

The arrival of the Switch launched while the PS4 was still selling strong.  It didn't cut into PS4 sales and there was a lot of overlap between the two with millions owning both.  The Switch did not compete with the PS4.  The PS5 on the other hand....

Switch won't compete with the PS5 either simply because the two are too different.

Switch cannot replace PS5 as it cannot offer the same big AAA games, but neither can PS5 replace Switch as it cannot offer Nintendo games or portability.

"Genesis won't compete with SNES either simply because the two are two different."

"Genesis cannot replace SNES as it cannot offer the same big games like Mario and Zelda, but neither can SNES replace Genesis as it cannot offer Sega games."

It sounds reasonable.  It's not remotely true of course, but it sounds reasonable.

SNES and Megadrive were similar traditional consoles competing for the same audience.

PS5 and Switch are totally different.

Both PS5 and Switch are both competing for the home audience.  The type of games selling the Switch are not that different from the N64 and Gamecube: 3D Mario, 3D Zelda, Smash Bros, Animal Crossing, etc....  The core games on the PS4 and PS5 haven't changed much since the PS1 and PS2 era either.  Sony and Nintendo were competing then, and that is why they are competing now.

Because the focus is expanding the market. Ex-players and new players. 

There will be overlap with many buying both, just as there is now, but not direct competition, because Switch can never offer all the big AAA games and therefore cannot pull that audience away from PS5.

If the two competed, they would be competing now, with Switch pulling sales away from PS4. Nothing will change when PS5 takes over because the situation will still be the same, with all the big AAA games on Playstation.

Are you going to keep giving me this obviously wrong argument?  If you are going to keep repeating yourself, then I suppose I will have to as well:

The arrival of the Genesis launched around the peak of NES sales in the US.  It didn't cut into NES sales, and their was a lot of overlap between the two with millions owning both.  The Genesis did not compete with the NES.  The SNES on the other hand....

The arrival of the PS1 launched while the SNES was still selling strong.  It didn't cut into SNES sales and there was a lot of overlap between the two with millions owning both.  The PS1 did not compete with the SNES.  The N64 on the other hand....

The arrival of the XBox360 launched while the PS2 was still selling strong.  It didn't cut into PS2 sales and there was a lot of overlap between the two with millions owning both.  The XBox360 did not compete with the PS2.  The PS3 on the other hand....

The arrival of the Switch launched while the PS4 was still selling strong.  It didn't cut into PS4 sales and there was a lot of overlap between the two with millions owning both.  The Switch did not compete with the PS4.  The PS5 on the other hand....

SNES/Genesis/PS1etc have nothing to do with Switch/PS4/PS5. You're too focused on trying to force past historical patterns onto a situation where they are not relevant.