Yeah, I agree that Tai and Mimi's Tri designs are better, though I don't find their new designs terrible either.
Well what really bugs about Tai's design is that they had to change his hair colour to something of more darker shade, which looks quite odd, Like what? Tai's hair colour has always been a lighter shade of chocolate brown since the 1st series, it's something we are just basically used to seeing him with that, it suits him well. It's especially Tai's hair which has been always a really notable aspect of his appearance and is pretty iconic in terms of appearance too. The fact that they had to mess with Tai's hair colour of all things in this new design is what really annoys me here.
Also, the sharpness in his looks is also a bit lacking here IMO, compared to his previous designs, as the main face and the leader of the Digidestined, that sharpness factor in Tai's looks/appearance is something I feel which is quite important, as it adds somewhat of an extra appeal.
And regarding Mimi...oh well, character wise Mimi has always been pretty much least favourite Digidestined among the Adventure Digidestined, I always tend to find her whiny, attention seeking and complaining personality really annoying, so the only ways she actually really appeals to me firstly her Digimon's Digivolution/fighting moments, and looks wise, she has always been one of (if not the most) cutest/prettiest among the Digidestined, especially in Tri, where she looked really stylish, fashionable and sleek, which had an extra appeal to me appearance wise. But in her new design here, that fashionable and stylish aspect of her appearance which she had a lot in Tri seems to be vanished mostly, which actually I find quite underwhelming here.
Being honest, I never actually watched the last movie. I spoiled myself its entire plot before I had a chance to watch the film, didn't find it very good and ultimately decided not to bother. Though I have to give the writers credit for actually killing off Meicoomon, I honestly didn't expect them to go through with it.
I see.
Well I'll say that you could maybe give the last movie a try, I personally thought that it was quite good for a climax/finale of a movie series, consisting of some really intense and epic action intermingled well with highly emotional moments as well. Apart from being intense, the action scenes/fights were quite superbly animated too, with Omnimon Merciful Mode's appearance being really prolific and narratively fitting for its moment; also the moment when Kari says to Tai that if he took the desicion to destroy/kill Meicoomon, she'd never forgive him personally, but if he took the decision adamantly amd firmly for the sake of the protecting the world, she'd do everything she can to help him in the cause, just subtly adds to the emotionally and morally intriguing factor in that whole final fight. In addition to all this, another thing which I found quite intriguing in this movie as the final climax is that how it took an took a more darker and serious approach overall compared to what we see usually in the Digimon anime, we saw someone like Nishijima brutally bleeding to death, something which we used to see in more traditional anime shows + that it took the desicion to kill Meicoomon in the end, which was a departure from the usual cliche happy endings we are mostly used to having in a show like this, that all the main characters are supposed to survive and live in the end, it gives a really subtle bittersweet touch overall to the ending which lives you at the same time slightly melancholic and yet hopeful.