I personally find that in TFT I don't get enough time between rounds to figure out which items upgrade into what, remember what items I need for which champion compositions. And let's not forget you need to figure out the composition itself on the go. On top of that you have to manage the champions themselves (buying, selling, upgrading) and manage the formations... A dozen of seconds is not enough for all that.
New players will always have to alt-tab (if you don't have several monitors) to check the guides on the internet. You cannot pre-plan everything. And current amount of time given is just not enough for that alone.
The timer should be twice as long, at least. And I don't care that you are pro. This should be comfortable for everyone and so it's better to have more time than not enough.