There are many of us who already believe Fr. Seraphim is a saint. For those who would demand to know 'why?', we must be careful that we don't fall into the Western reasoning. That is to say that the Orthodox Church doesn't have a list of criterion and an investigation team to verify said list. But as for myself, and a great many others whom I have spoken with regarding his canonization, we feel it in our hearts.
I agree with the first part of what you say, but we can go into a bit more detail than just saying we feel it in our hearts. I would say I'm not alone in believing that reading Fr Seraphim's writings helped significantly in bringing me to Orthodoxy. There are other native-English speaking Orthodox writers which have helped me, and help others - Metropolitan Kallistos being a good example - but I'll be honest in saying that there is a certain urgency in Fr Seraphim's writing that was compelling. I'd also say his writing was simpler and more straight-forward too, and I mean that as no slight on either Fr Seraphim or Metropolitan Kallistos. Given that, it doesn't surprise me that Fr Seraphim's works have been translated into Russian and Greek even though there's already a wealth of spiritual Orthodox writings in those languages already. He's added to this Orthodox treasury, without inventing anything new.
person as a Saint doesn't automatically mean that all their writings are considered "canonical", so whilst I appreciate concerns regarding Fr Seraphim, I don't think it's an issue. Totally divorcing the person of Fr Seraphim - the ascetic and spiritual guide - from the things he wrote is to ignore how
Fr Seraphim helped bring a lot of people in the west to Orthodoxy. Fr Seraphim died before I was born, and the first contact I, and many, had with him was not through directly experiencing his intercessions, or really looking at the example of his life - all that comes later; the first contact with him, and often with Orthodoxy, is through his writings. So they're definitely part of the "why" he is recognized as a Saint already.
ps: In my last post I mentioned the people he referred to in his writings, who have since been universally recognized as Saints. I forgot to add, of course, St John of Shanghai and San Francisco, Fr Seraphim's spiritual father, who was not canonized until many years after Fr Seraphim's repose. I just think it's interesting and (perhaps) revealing that Fr Seraphim recognized and drew upon the wisdom of these Saints before they were ever officially recognized as such.