We HAVE to get them in a raid? That's so stupid! Raids are pretty much designed to screw people over, because only 1 Pokémon can Dynamax at a time and the Raid Pokémon can't be caught more than once. Not like the Switch has speakers either, so you can't communicate with anyone outside of a phone or a computer and even THEN you need their contact details.
The reason why GO works is because you literally travel to locations with other people IRL and one raid Pokémon can be caught more than once.
First off, it has already been stated that you can do Dynamax Raid Battles by yourself with three filler NPCs, so you don't have to worry about having to coordinate with other people.
Secondly, after reading some more, I've become confused as to the matter of Gigantamax Pokemon. I can't tell if it is that only the Pokemon caught in Dynamax Raid Battles that will be able to Gigantamax or that you can only catch Pokemon that can Gigantamax such as Alcremie, Corviknight and Drednaw through Max Raid Battles and not through normal wild Pokemon encounters? Until Pokemon clarifies, I'm now stumped as to which one it is...
Edit: Nope, nevermind, it's the former thats correct. On the Pokemon website it states "Regular Drednaw and Corviknight can Dynamax, but there are some special members of these species that can Gigantamax. You can catch Gigantamax Pokémon for your team by participating in Max Raid Battles, but it seems they’re very rare—finding one won’t be easy!" This means that, unless Hyper Training comes back, Gigantamax Pokemon may very well be competitively useless.