If that's the only thing you play online and with how shitty the From games can be on console, PC is by far the best option for you.

And yeah, online play should be free, I agree.

I'd recommend making the jump from a PS4 to a PS5. The graphical bump alone would be like jumping from a GTX 770 to an RTX 2070. The SSD is nice and the PS5 is backwards compatible with PS4 games.
But first and foremost, I'd recommend getting a nice PC instead. If you have the cash, then you can buy what will more or less be the equivalent of a PS6 right now.

I'm changing my answer, I would recommend a PS5 upgrade to a PS4 player, PRO or not. Simply cause the PS4 games run better and the system is enhanced in QoL ways to justify it with the newer games being the icing on the cake. I'd just give a warning that many of the newer games may be broken and overpriced, stay 6 months behind the curve for price cuts and post patch content and make sure to research every title both from critics and users.