As a heads up:
Shield Version players can get the Great Ball Guy T-shirt now. I just tried it myself.
Plus he takes so long to set up his weather effects that he's very easy to beat (the AI and the types of the Pokemon he uses don't help)
I think he's supposed to be pretty easy to beat for people like you and me, since the main audience of Pokémon games are small children. They need to make it such that even they can beat the game and feel powerful and accomplished, and Game Freak has spent a lot of thought scaling the difficulty over the generations to address problems that come up when kids who don't think ahead and don't strategize (and older people who might think the same way) got stuck in past generations.
For instance, I remember a demo for
Pokémon Yellow in which someone who played the game from the start got stuck at Brock, as they sold off all of the Poké Balls given to them and spent all of their money on Potions. They were able to brute-force past Brock's trainer but could not find a way to overcome his Onix. There have also been many cases of people who found
Pokémon Let's Go! too hard, as they had just come out of
Pokémon GO and were struggling with the concepts of turn-based battling, moving their character around, using HMs, and type immunities.
Rather, I see the single-player mode as one long tutorial on how to battle more effectively while providing a sort of wish fulfullment. Raihan is the sort of boss character designed to teach you about a mechanic--namely how Sandstorm works and how to fight with it up, as well as illustrating how double battles require a different kind of thinking than single battles. If you go into the game completely blind, Raihan will be trouble because your team was probably not designed for double battles, and your Ice-types and Fairy-types won't be effective against his Duraludon (which, if you're playing the game blind like that, you won't even know what Duraludon is until he sends it out). But he won't be so much trouble that you can't beat him even with no prior knowledge, just one that you have to pay attention while battling.
Garbador briefly bids farewell for Sword players (and Copperajah for Shield players) with the Easter holidays granting players access to various baby Pokemon and most importantly, Ditto. If you are looking for a good opportunity to get good Dittos for breeding (have got a few 6IV Pokémon from the event Raids) now is the time.
I'm still seeing Gigantamax Garbodor, Charizard, Copperajah, and Duraludon raids on my list, and I'm still finding them in my dens, so they're not gone. It would be odd to see them go away after two weeks anyway; they've all been at least three weeks long, with most being about one month.