It is. What I mean is have Brexiteers thought out how to deal with the Irish border, which most likely is going to be hard border with customs checkpoints and what not in the case of no deal.
What to do with the customs duties, tarifs etc. for the imports UK is pulling from EU (out of all UK imports over 50% are coming from EU market). How about possible tariffs all UK exports to EU might have? Do buyers in the EU want to pay the increased prices that customs duties will bring to the UK goods, or do they look cheaper alternatives from elsewhere. Currently out of the UK exports about 40% are going to other EU countries.
Trade numbers pulled from here: https://researchbriefings.parliament.uk/ResearchBriefing/Summary/CBP-7851
There’s lot of pros Brexiteers are listing that will be beneficial in the long run, but tbh they are as problematic and “big ifs” as are all the cons involved in no deal situation.
And just to clarify most of my pessimism towards Brexit comes from my work experience. I just see daily how much easier the trade is with other EU countries because others are playing with the same rules.