Honestly, I really like how the Tzimisce are being portrayed in V5. This probably comes down to me being in the minority of people who prefers the Dracula styled Tzimisce over the transhumanist styled Tzimisce, sorry people but it has always been Vladimir Rustovich over Sascha Vykos for me.
I love that they merged the main clan Tzimisce with the Old Clan, imo I have always found the concept of the Old Clan Tzimisce being a bloodline without Vicissitude to be kind of dumb. I have always thought that from an in universe perspective that it made more sense for the Old Clan to be a ideology not a bloodline, being that a "Old Clan Tzimisce" is pretty much just a elder Fiend that does not adhere to the teachings of the Eldest and the Path of Metamorphosis and simply either uses Vicissitude as a tool and not for enlightenment/evolution or completely neglects the use of Vicissitude out right which, we pretty much already see with a lot of Tzimisce in WoD already, with Fiends like Vladimir, Radu, Lambach and of course Vlad Tepes.
That being said I do agree with some of the complaints about the changes to the clan. I do think the Tzimisce losing Auspex for Dominate is a shame, I personally think that Dominate does fit the Tzimisce flavor however. I don't know but being able to command the beasts and people of your lands just screams Tzimisce to me but I can see how people might think it takes away some of the clans flavor. The thing that separates the lordship of Tzimisce to the Ventrue and Lasombra is that those clans control and dominate to get there way while the Tzimisce simply rule through fear alone, so I can see how fans could think that the Tzimisce getting dominate goes against the clans flavor but I disagree.
First of all you can still play the stereotypical Tzimisce that rules through pure terror in V5 and a Fiend only needs to invest a little in Dominate anyway. Get which ever power you prefer for Dominate 1 then snag Domitor's Favor for Dominate 2, then just invest in intimidation and Vicissitude and you are pretty much the classic Tzimisce Voivode. The complaints I do agree with however is that the removal of Auspex does remove the spiritual side of the clan, which I wholeheartedly agree with.
I have always viewed the Tzimisce as a clan having 3 sides to them or more fittingly the the clan is a Dragon with 3 heads. The Overlord, The Transhumanist, and The Sorcery, in earlier editions my main problem with the clan was that the Transhumanist aspect of the clan was emphasized the most while the other sides of the clans were neglected. But now it seems that V5 is leaning in hard to the overlord aspect of the clan, which again I prefer personally but I still want the transhumanist and mystic aspect to be represented to, since they are still a equally important aspect of the clan. Hopefully with the V5 Sabbat book coming out in the future, we get some more representation for the Kolduns and Metamorphosis Tzimisce. Maybe a Koldun loresheet which gives Tzimisce Blood Sorcery and or Auspex and Koldun rituals. And a Metamorphosis or even Yorak loresheet that really doubles down on the transhumanist elements of the clan.
TDLR, V5 Tzimisce is a good start and a nice take on the clan, they just need to show some more representation to the spiritual and transhumanist side of the clan along side the overlord side of the clan. Sorry for the long take but I just got a lot to say about the Tzimisce lol.