Reasons are fine, but if a business don’t adapt to regulatory or market changes than that is down to them. Obstacles and challenges are thrown in our paths everyday. A good team will deal with that and use it to their benefit. Many other organisations, and countries have been preparing and dealing with it. Both within the UK and outside the UK.It's not about blaming others, steel is highly competitive, if your margins are lost because of additional tariffs, that is as you say, "life".
But if the reason why it is no longer profitable is because of these (potential) tariffs, and these are related to Brexit, the reason is Brexit.
No one is blaming, they are stating facts which some people don't like.