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An excellent RGG "side game" that I would say is good enough to, lower content aside, to stand with the series' best entries. Some bullet points to give you an idea of what's going on with this weird new Joryu guy:

This game is much less focused on main campaign content, and more focused on side content. It's got less than half the campaign length of a regular RGG game, and even that's being a bit generous as a significant part of the main story is actually more like mandatory engagement with that side content. If you're like me, you can easily get 60h or more out of this if you like Yakuza minigames or the improved Colosseum, if you're just doing a one and done campaign this is more like ~20 hours. (maybe plus a few more if you want to play 8's included demo)
This game is not a good entry point for those new to the series, and isn't trying to be. This game was made for people who have played Yakuza 7, and are invested enough in the Kiryu Saga games that they want to know what he's been up to during the transition between Y6 and Y7. IMO Yakuza 0, or maybe Yakuza 7, are better starting points for anyone looking to try an RGG title.
The updated combat is overall very fun and much better than some other Dragon Engine games like Kiwami 2 IMO. I don't think it's as good as Lost Judgement but that's probably an unfairly high standard to clear. Joryu struggles to earn Heat, but makes up for it by being very good at opening enemies up to air juggling and having perhaps the strongest crowd control in the series' history.
While the Yakuza combat style plays how you'd expect, Agent is a new moveset that gives Joryu a lot of crazy new tools. Some of its ideas, like the ranged grabbing wire are extremely useful tools you'll use often, but some other features like the Hornet drones don't feel anywhere near as useful. It's great for defense and crowd control and so always has a use, but I think most players will use Yakuza style as their default with Agent being a specialist style.
The improved Colosseum is probably the best take on the feature we've ever seen. Besides the usual ability to quickly enjoy fights, you can also assemble a custom team of fighters for giant chaotic teamfights and, finally, play as said fighters to use their unique movesets and abilities normally reserved for NPCs. Because this is still a side game, it's not perfect. For example, Kaito only recycles Yakuza 0's Brawler moveset instead of his full Kaito Files moveset, and Higashi does not inherit his unique Muay Thai moveset from Judgement. But we do get some classics like the joke drunkard moveset, and overall a really fantastic way to make our own fun trying to become world champs with jobber characters. My only real criticism of the Colosseum is that some of its later Hell Team Rumble fights are a bit much, bloating HP to comical levels (seriously some of these enemies have like 50 health bars to work through) because their captains are balanced around requiring an entire levelled team of 10 people dogpiling attacks onto them like an MMO raid boss. Aside from that balancing complaint that only affects a small portion of the Colosseum's content (and will become less of an issue further and further into endgame stats) I think this is a huge highlight feature especially for longtime fans.
Despite how relatively short this story is, it is definitely worth the ride, for the ending alone, but even the stuff aside from that is extremely fun, especially the final boss.

If you have any investment in Kiryu's story and can spare the price, (which is admittedly steep) you really, really should play this.