> Why would sellers need to pay up to 6% to a realtor and buyers pay thousands in closing costs...because there is a disparity in access to information.

None of the type of information disparity that realtors help with are going to be solved by blockchains. Perhaps you could eventually build a better title system, but title-related expenses are a tiny portion of closing costs and there are reasons for the complexity.

The biggest portions of the closing costs that aren't directly related to the lender's pricing or real estate commissions-- title insurance-- can't go away anytime soon because the claims they protect against can be decades old. So even if you had a perfect title system today (which seems really hard) and everyone moved to it instantly, we'd still be stuck with those costs.