Yeah I get it, you are going to have to make decisions as to what cards really offer the most value. I don't disagree on this, but my view is if you do this you will not be disadvantaged. In my view the advantages offered by churning outweigh the disadvantages you mention and if for you they don't the answer is simple, don't churn so much.Easier to churn yes - if focused solely on getting an approval. But also harder to manage the overall churn process, and with a likely loss in functionality.
If one has an Amex Platinum Edge card earning say around 60,000 points a year, another much lower point earning card for all other payments, and a card for foreign exchange free overseas purchases - it is going to be kind of difficult closing those useful cards, and reducing them to one or two new ones while making sure that bills are paid (e.g. phone bills, health insurance bills, water bills etc etc). Some of the functionality afforded by the current useful cards will be lost if one wants to maintain the churn activity.
Regards,
Renato
To reiterate what some on here say quite often, those who understand the game and play it best get the main benefit.