The main concern I'm hearing right now: What if new COVID variants keep evolving so much that vaccines can't keep up and we end up in a situation like the flu?

It's possible, but I think it's unlikely. Here's why:

The flu has 2 advantages:
1. Other animals can be reservoirs, so even if you stop it in humans it could go back from them,

Do you remember avian flu? Swine flu? Animals that carry the flu include ducks, chickens, pigs, whales, horses, birds..
https://www.cdc.gov/flu/avianflu/virus-transmission.htm#:~:text=Influenza%20A%20viruses%20have%20infected,subtypes%20of%20influenza%20A%20viruses

Meanwhile, so far COVID has only been witnessed to easily jump between humans and minks AFAIK. There's not much data on this yet, but it's very hopeful

2. The flu mutates much more quickly than COVID
It took 50M cases (and probably hundreds of millions of infections) for COVID to mutate in 3 bad variants. It's much slower.

With the current vaccines + herd immunity, the speed of mutation will slow down: fewer cases, fewer opportunities for mutations.

Meanwhile, vaccines are amazing. It took 1 year to approve the Moderna vaccine, but only 2 days to create it. The rest of the year was testing and approval because this was a new technology.

Moderna likely already has vaccines for the new variants. And now that the tech and vaccine are proven, it's likely that they can test them and get approved in a few weeks rather than many months. Once tested, they can create a vaccine that covers all variants at once.

At the same time, Moderna and others are ramping up production and are making deals to share production with other cos. With + production capacity, they can probably ramp up production and distribution much more quickly too, sending it to the world quickly

Slower mutation rate, higher vaccination rate, and few external reservoirs means I think we can eradicate it