There is a lot of overlap here between the S&P 500 and this fund. I've attached an overlap PDF here to give you an idea. 88 of ADX's holdings are included in the S&P 500, and outside of some very small allocation tweaks, it looks like for the most part it does just hold a big chunk of the S&P.
I would say this fund isn't an outright closet indexer, but it's pretty close. By closet index I mean they build a fund, largely mimic the holdings inside of the S&P 500, and then charge a higher management fee.
The only benefit here is it aims to pay out quite a bit of its capital gains and dividends as distributions.
I don't see a ton of value of owning this outside of the S&P 500, unless you are insistent on the higher income.