I only used it during the pandemic after doordash premium freebies ran out and amazon offered a free year sub. The fees and prices were effectively the highest and they NEVER offered promotions. Meanwhile ubereats is over here spamming me every other day about 60% off orders which comes out to something like 10% less than what I would normally pay if I went and picked up the takeout myself. Even doordash offers some small promotions that mostly just eliminate all the middlemen fees for an order or two rarely.
The fees on these services are enormous and we're just talking the tech part of it - they're taking 30% from the vendor, they're charging us another 5-30%+, and then they are paying a delivery driver sub-minimum wage with the expectation that we will tip (mandatory bribe) the couriers to deliver the stuff because nobody takes an order that doesn't have a tip applied. I honestly have no idea how they think they are providing value by being leech-like middlemen to the whole process. The whole thing feels like something that could be open sourced and run by a nonprofit in terms of infrastructure, and then it would be up to stores to handle the customer service, payment and driver cost.
As a bonus, GrubHub forces you to tip before delivery, when you're placing an order. Unlike ubereats you cannot adjust the tip based on service without contacting support and having them adjust it. It's not a tip at all, but a bribe that says "please actually take my delivery order."
The bottom line to me is delivery fees on top of the inflated prices way above and beyond in-store or first party delivery, the enormous tip, the vendor fees and the frequency of mistakes or extremely long delivery times make this kind of service not worth it as a customer. If the fees were flat it would at least make some sense to do relatively large orders rarely. That's not even the case though, you're just charged way more for the same effort from all parties except for the restaurant.