Yes there are challenges with adoption. Limiting the transaction capacity will not help.
It is a very stupid argument. Saying that current block size is limiting adoption is like saying a place is not attractive to people because it's overcrowded...
If only 3 people can send a transaction per second, then how do you expect 50 people to send a transaction every second (this is roughly 2.5% of what Visa does)?
To be fair, if Visa just throttled its throughput to 3tps, people would be forced to pay a hell of a lot more per tx, all the spam Visa transactions would disappear in the Free Market, and Visa would become the new gold standard.
No. Because of how the Visa network is setup merchants would receive significantly less of each transaction to the point that the majority of merchants will no longer accept Visa. After the majority of merchants stop accepting Visa, consumers will have less of a reason to use a Visa branded card, so banks will stop issuing them. This would mean that the overall usage of Visa will decline significantly, as will the Revenue of Visa.
Those that are still accepting/using Visa will need to wait hours/days for their transaction to be processed and most of the time the merchant and customer will likely agree on another payment method while the transaction is still processing.
I cannot think of any logical reason why someone who wishes for Bitcoin to be successful would not want to allow more transactions to be processed via the Bitcoin network.