Not sure where some people get their info here but a ton of it is wrong. Platinum is not the top tier on Delta, Diamond is. Platinum does not get you into the Delta Sky Clubs, Diamond does although you can choose 4 day passes as your Choice Benefit once you get Platinum. Gold and Platinum get a discount if you want to purchase a Sky Club membership.

Once you get to Gold or higher, you get status on Skyteam which is the alliance Delta is part of. This gets you increased baggage allowance on other Skyteam members and use of their lounges IF you are flying with them internationally.

Medallion used to be worth it and I was one of those people who do a mileage run or two to make sure I got at least Platinum since that used to be when upgrades started becoming more frequent, but those days seem to be going away quickly. Gold or silvers really have to fly odd routes on off days to get upgrades since Delta introduced First Class Monitization where they offer cheap upgrades at check in, reducing the number of first class seats available to Medallions.

ALL frequent flier programs really enhance the flying experience, especially if things go wrong, however they are constantly being devalued and airlines are constantly trying to figure out how to take features away and charge fees, nature of the game these days.

Basically getting Medallion gets you perks like first class upgrades, no baggage fees

You do get into Sky Clubs as a platinum for free on international travel...done it multiple times.

Another benefit is the faster check in line at the counter.

At many airports, platinum gets you through the express security line. Saves a lot of time at Honolulu doing this....of course the TSA pre-check is even faster...