Off base (going by core rules), anyone can make a medicine check to stabilise a dying creature (dc 10 usually, unless there are other complications); this doesn't get them up - they'll still be unconscious for a few hours, unless they receive other healing, but it does protect them from having to make any more death saves, unless they take damage and begin dying again.

A healer's kit has a number of uses (10) before it is used up, and can be used by anyone to automatically stabilise a dying creature without needing to make the medicine check. Someone with the Healer feat can also uses a charge of a kit to restore hit points - not many, but some. This means that someone with the Healer feat and a kit can use their action, and a charge of the kit, too bring a downed character back up into combat, in a inch... but it requires both of those things; a feat investment, and a kit with charges available. Though this is functionally similar to using a healing potion, kits have 10 charges, for a fraction of the cost, and can generally be purchased very easily compared to healing potions (usually).

In a video game translation, this could be smoothed out and made more player-friendly; [[This is Just One Possibility - It Could Be Done Many Ways]] One way we COULD do this would be to have the help action automatically stabilise, while someone with the Healer feat restores a die of hit points whenever they help a downed creature. Like that, you *could* get to the ridiculous conscious-popping circle spam invulnerability situation, but everyone would need to invest a feat in doing so; some players might swear by it as a safety net, others would not feel compelled to use it at all, and view the investment cost as too high to justify, and others may take the feat on one character, as a character/insurance choice... and if the people taking it or leaving it is a varied spread, then balance has done its job.