..... especially today.
It is very true that we have fabulously low interest rates on mortgage loans but buyers do need better credit than they did a few years ago and even if the credit is stellar, it still takes much longer to get a transaction completed if the buyer is going for a loan rather than using cash. So, as long as the differential isn't too great, generally if you have 2 buyers on a property and one is going for a loan but is offering say, $10,000 more than the one who is offering a cash deal (for example on a $300,000 house), the cash deal is probably going to win over in the mind of the seller.
Financing is only part of it though. There may be other contingencies that could sway a seller in one direction or another... for example if there needs to be a radon mitigation system installed in the home and one buyer says they'll pay for it ( a cost of maybe $1,300), that could seal the deal in their favor regardless of financing... you get the drift.
The fact is that regardless of the perception of real estate transactions, that they're simple, they are not. There are many aspects of a deal that may not have even been considered many years ago, like buried oil tanks, or high tension power lines etc., that do have an impact. That is one reason of many why, if you are EITHER buying or selling, make sure you have a professional real estate agent assisting you and giving you the support that you need.