You need two more points of comparison, to perform a reasonable evaluation: Taking a short rest without casting Rope Trick, and casting Prayer of Healing.
OK, let's consider those.
Rope Trick doesn't let you recover resources. It just allows you to exchange your existing resources (time and hit dice) with greater reliability. It increases the viability of taking a short rest in dangerous locations, where a short rest might otherwise be interrupted. But you spend the spell slot, and it doesn't actually make the rest take any less time, or give you any greater benefit from the hit dice you spend.
Exactly true. You have those HD with or without Rope Trick, however, when you are in a dangerous location tends to be when you need them most, and when they are the most difficult to access.
In a standard dungeon crawl, it can be extremely difficult to take a short rest. That's when Healing Spirit becomes so useful, and also when Rope Trick becomes so useful.
Tell me if this sounds familiar, your party is in a dangerous location, you can't reliably take a short rest, so you use up more resources as you can in between encounters until you have escaped or cleared the dangerous location. You don't have a time limit, but you simply aren't going to get an uninterrupted hour to rest. Then you end that part of the adventure, you are assumed to take a long rest, or many long rests, with the HD available on Short Rest never spent.
If that does sound familiar, then I would suggest that although your character had those HD, it was no different than not having them, since they were inaccessible.
I would also suggest, that in many cases, if they had been accessible,
you wouldn't have needed additional between combat healing. This is when Healing spirit becomes most useful, when a short rest cannot be taken. It is also when Rope Trick is most useful, for the same reason. Now certainly some situations exist where there is an unseen clock ticking, and it's the hour long resting time that makes a short rest inaccessible, and yes, a Rope Trick can't help you there, but I'm sure you would agree that there are also situations where there isn't an invisible clock ticking, but taking a full minute to execute a Healing Spirit is dangerous out in the open.
Prayer of Healing is the currently existing out-of-combat group-healing option. It directly converts spell slots into healing. Out of combat, it does what Healing Spirit does; and it establishes the baseline for how much more effective out-of-combat healing is allowed to be, compared to in-combat healing. The comparison is direct: Healing Spirit is ten times faster, and heals five times as many HP.
That might be your experience. In my experience, the spell Prayer of Healing, though I've seen Clerics take it, and even offer to cast it, has never been used in my gameplay. Never.
Usually we have one or two party members that have taken the majority (or often all) of the damage. Now, just for example, let's say we cast Prayer of Healing. A 2nd level slot is used, and a total of 2d8+3 (assuming pre 4th level), or 12 points of healing to 2 targets. (24 points total). This requires 10 minutes.
It's almost always better to swallow some goodberries. 2 first level slots (2 slots total) heals 20 HP, except without requiring the 10 minute cast time, no worries about interruption, and those Hp can be distrubuted as needed (for example, if one player took all the damage).
Of course, Goodberry isn't intended to compete with Prayer of Healing. It's intended as a long term food source, and 10 mini 1 hp heal potions.
This illustrates just how bad Prayer of Healing is.
Is it possible the developers know how bad it is too?
Look at the Ranger. Xanathar's was clearly intended to fix some of the problems with bad Ranger options by offerring different excellent options. The worst of the Xanathar Ranger options is likely better than the best of the PHB options. Do you think that was a mistake? I don't.
Could it also be that the developers realize that Prayer of Healing fails to perform the function it was intended for, and therefore have little concern if another spell eclipses it? I can't say, I don't know the minds of the developers, but I would hope that is the case.
Healing Spirit gives benefits comparable to a short rest (with some trade-offs), at the sole expense of a spell slot. You spend only a spell slot, and everyone heals as though they had spent five hit dice, except they don't have to wait an hour or actually expend those hit dice. This is egregiously out of line with every other healing spell in the game.
Let's go back to my previous example, and let's look at a 3rd level party. We have a Fighter with a Con of 14. That fighter has 28 HP. We also have a Paladin, the Paladin has a Con of 14 too, also has 28 HP.
After a particularly nasty combat, the Paladin dropped to 10 HP, and the Fighter actually went down (brought back up to 4hp thanks to the Bard's healing word spell).
Now we have a Circle of Dreams Druid. This is a healing master. That Druid casts Healing Spirit and heals both back to full (we have 10 rounds uninterrupted in this scenario). That's 18+24 HP healed, or 42 HP.
Except the DM banned Healing Spirit. So instead the Circle of Dreams Druid hands out 40 goodberries. They used 4 first level slots rather than one second level slot. Yes, I would rather burn the second level slot, but lets dispense with the 10x more healing in 1/10 the time nonesense when comparing it to Prayer of Healing.
Rope Trick doesn't let you recover resources. It just allows you to exchange your existing resources (time and hit dice) with greater reliability
Here's how I would like to finish up. With a thought experiment.
Your party is walking along a river filled with healing water, but you don't have a method to draw the water.
I cast a spell that gives creates a jug, you draw the water and drink, healing yourself.
Does it matter that it wasn't the jug that provided the healing?
Maybe you are using all your short rest HD and needing even more healing inbetween combats. That could happen. Especially if you don't have a god wizard in your party preventing that massive re-occurring damage. If that is the case, isn't your DM being a bit of a sadist by not allowing Healing Spirit then?