Healing Word's fine. I might view it as a problem if it was handed out to half casters, who where going to be using their action to attack anyway, but for the overwhelming majority of Bards, Clerics, and Druids (the classes who get it), using Healing Word vs. Cure Wounds still means that the main thing they are doing with their turn is casting a level 1 healing spell, they just still get to cast a cantrip or make a weapon attack. There are optimized edge-cases where this is still devastating, but optimizers are going to optimize.
If there is a problem it is that the additional healing from Cure Wounds is too little to be worth using instead. It's not worth moving to the fallen comrade and using an action rather than a bonus action just to get them an average of 2 more hit points per spell level. If I was going to change the low level healing magic regime of 5e D&D, it would probably be to give beneficiaries of Cure Wounds the opportunity to burn hit die for extra healing. I think a fair number of anti-Healing Word people's real objection is that they want the main level one healing spell to be Cure Wounds, because that's what it was in all the other versions of D&D they've played, and in 5e it's the trap choice for anyone who can take Healing Word.
I will say I have really only found the up from zero system of 5e frustrating or irritating in one situation, and that is when I am playing the video game version of the ruleset, Solasta: Crown of the Magister and all the enemy behavior is preprogrammed, combats go by quick, my level of investment in characters is negligible, and I can restart from the beginning of combat at any point. The habit of enemies there to leave dying enemies alone, but prioritize prone but just healed enemies, also just results in a lot more whack-a-mole than I've ever seen in real table play. At an actual table, when actual characters are even slightly at stake, death is a nontrivial event, the DM is able to sometimes go easy on the just healed PC or up the tension by going for killshot on a dying one, and, you know, people are roleplaying the relatively lax rules for rescuing someone from zero don't bother me, and seems a reasonable concession to letting everyone stay in the game and not chaining people to a healer role.