Pros:
1. Visually enthralling VFX: this movie has set the standards for future movies to come in terms of VFX in films.
2. Hair-raising BGM: the BGM, especially the ones accompanying the Astrās, are very impactful and tastefully placed.
3. A storyline that has the potential to make India's own superheroes: mythology is something that is a very important part of our Indian heritage and, thus, this concept of Astrās can be filled with world-class lore and characters if well developed. The spark has been lit and Ayan Mukherji has the opportunity to leave his mark on the industry (maybe even the world) with this Astrāverse.
4. A wonderful and completely unexpect surprise cameo in the first 15 minutes of the movie: it sets up the movie perfectly and succinctly shows the two sides who will be at war.
5. Awesome performances: Amitabh Bachchan and (surprisingly) Mouni Roy brought their characters to life in their performances. Nagarjuna has a small, albeit a very impactful role that he pulls off with the experience and practice, the hallmark of a seasoned actor.
Cons:
1. Excessive and horribly paced romance sub-plot: the romance between the male and female protagonists forms a very important (albeit unnecessary and blazingly rushed) part of the story. But it is done horribly with terrible dialogues written to force the chemistry between the two. Removing 60% of it to expand on the Astrāverse would have earned this movie a lot of more praise, critically and publicly as well.
2. Terrible screenplay: an example would be that in the movie the leads have to travel to Varanasi to protect a certain individual from the antagonists but they first spend a few days in Varanasi romancing to Kesariya, wasting precious time which could have been useful in protecting the aforementioned person from the villains.
This is the most egregious example I can think of but there are more.
3. Ridiculous dialogues: the core concept of the movie is that the fate of the world hangs in the balance and this gravitas is not reflected in the protagonist's interactions with the people in the Astrāverse. The dialogues try to be needlessly funny, irrespective of the situation at hand, and this breaks the intensity of the movie and any immersion the audience might have felt building up, not just once but multiple times.
4. Lackluster leads: Shiva is written like Ranbir's characters from YJHD and Wake Up Sid, and not someone mature enough to take the mantle of the Earth's protector. And Isha's character is nothing but a passive love interest with no agency or goals to achieve other than loving this man she met barely a few weeks ago making her entire existence nothing but a damsel in distress who has to be saved at all times by people who can handle the Astrās.