If FedEx's platform can't promise 1 or 2-day delivery, it will never take off.
On the other end of the spectrum, Amazon promises 1-2 day delivery but has been falling through more often than first seen and can become a 2-4 day delivery. Amazon does seem to absolutely bleed their workforce to keep up, but also push more absolute junk through their platform now.
Costco is in kind of a prime position to offer quality-tested products with 1-2 day delivery... but they just do not care to offer this "Prime" type of service. Costco is still quick, just not as quick, and their website / app is trash to use compared to Amazon.
One honest competitor I see rising up - Home Depot. They are making incredible moves in this space (in terms of web/app UI/UX and expedited deliverable date).