Would you use a product that showed you historical data of your crypto wallet?

It depends what you mean by "wallet data," and also what the utility of the product would be for the user. There are numerous apps that connect to your bank accounts, and some have garnered millions of users, so the practice of linking your banking data is fairly common. I think it's a case where the clearer the utility of the product, the greater the comfort level of the user. It should also be especially clear that the use of the financial data helps make the product work better for the user.

I looked up etherscan. Are you referring to a cypto wallet? I think most transactions are recorded pretty clearly in any wallet, both crypto and non crypto. However, I think you can add value by making this a personal finance app that reads more friendly than checking a bank account. For example, it could gamify saving money to make it fun or set reminders for budgeting. Furthermore, you can offer more value with a blog and building a community around personal finance.