Was Irrfan Khan really that good of an actor?

Tbh no disrespect but I found him to be extremely one dimensional and someone who had no facial expressions and used to keep the straight face in almost all of the scenes regardless of the genre. Maybe I am wrong cause I have not seen his work in his critically acclaimed movies like Maqbool, Paan Singh and some others but I have seen his work in the movies like Life of Pi and a lot of other movies and it was ok nothing special

It would be better for you to see his work then...

I was watching Paan Singh Tomar recently and almost every other scene I thought he was amazing. His dialogue delivery is one of the best I have ever seen in Bollywood. 

Perhaps you should watch first.

I don't know how fair it would be to even talk about someone who has done such amazing works and is no more. 

He was a brilliant actor. 

Irfan khan was one of the Best actors we have ever had. There’s not a single movie of his which I have watched where I found his acting unconvincing or felt as if he wasn’t fit for the role.

That guy aced each and every character he played in each and every genre ... be it negative (Haasil), Romance (Lunchbox, Piku), comedy (Karwaan) ... Have you seen Talvar or Paan Singh Tomar or saat khun maaf or Hindi medium or take any of his movies for that matter ? 

His acting was anything but one dimensional!

As suggested by almost everyone else here I would also recommend you To watch his work first before getting into any conclusion and I am sure you’ll get to know why hardly anybody here seems to agree with you on this!

I used to find him overrated too. The thing is, I know Sonam was trolled for this, but I believe it too: if you're not good looking, you're considered a good actor.

Somehow, the "raw"/edgy physical appearance gives more depth and character to an actor's performance. 

However, I realised his immense talent when I watched more films. Check out: Maqbool, Hindi Medium, Angrezi Medium.

I hated him in most "hollywood" films, they don't know how to utilise his talent.

I always found him over rated 

He was one of the best