I try to be even handed, I apologize if something I said was taken the wrong way. I made that post before I realized people were so serious about this stuff. I meant no insult but I really see no good answer to what you want. Certainly not from a game like D&D which oversimplifies virtually everything.
I did try to make light of the situation in the shovel post, hence the "

". But you really would need a ton of info to know how much you can shovel. There is no constant. So if we had something along the lines of "you can move a square foot of dirt every minute" and I'm envisioning the heavy clay soil around my house that I need a pickaxe to break up before I can shovel much at all, that's not going to work. If I'm envisioning dirt that was recently excavated and quite loose or a sandy beach a square foot a minute is low. Heck, I lived in Arizona for a while, I doubt I could have gotten more than a couple inches with just a shovel.
Along the same lines I honestly don't know what kind of information or details people would need about a tent. It keeps you out of the rain, and provides a bit of protection from the elements. It's a piece of waterproof cloth between you and the great outdoors. The last time anything like that was covered was back in the TSR days in the Wilderness Survival Guide where they dedicated a page or so to it. But even then it was just a lot of detail that gave the impression of useful info but it was still up to the DM to decide the current weather. It just added a layer of complexity for the DM when describing the weather. The book also didn't stop the arguments, especially their description of what a "superior" tent entailed in my experience.
Which is why I was trying to end the conversation. I don't think the game rules should try to cover everything and IMHO they don't need to.
So first things first, I wasn't offended by what you wrote in that post. I did not think you meant anyone any particular harm in writing it.
That said, it is hyperbolic, seemingly on purpose as a good-natured mockery of a position you disagree with. A lot of posts on this board are this way, some of mine included. Describing it as such, to me, does not seem like it should be an insult. That was the full extent of concern with that whole interaction.
On to the important bit..the shovel. Here is what I ultimately come down to. Digging a hole or trench is an adventuring task. A magic spell and a shovel are both tools that can be used to accomplish that task.
The same factors: soil water content, hardness, tree roots, whatever you want, exist for them both. Both tools could very justifiably suffer from that litany of environmental factors, and the accompanying DM variance in how those factors impact the PCs ability to do whatever they are doing.
But one tool (the magic spell) provides clear guidance on what can be accomplished with it and the other tool (the shovel) provides no guidance at all regarding what can be accomplished with it. Same task.. Same environmental factors.. both tools.. unnecessarily different levels of mechanical guidance.
To be fair, I completely understand your hesitation to want to write out one specific performance level for the shovel. I've dug enough holes to know that some are easier to than others. But, if the equipment in the book is supposed to be helpful for accomplishing a task, the player should have some reasonable idea for how it should be helpful.
Can PCs dig a hole without a shovel?
Is there some kind of check to dig a hole?
Does the shovel help PCs dig faster/deeper/better?
Does the shovel allow them to dig in places they ordinarily wouldn't be able to?
The game doesn't tell us any of that, and it could. It's the same way with the tent and the other gear folks have been complaining about.
Personally, I'd collect a bunch of these types of items into themed kits that could provide clearer, more explicit benefits to a party of adventurers without needing tool-level mechanics.
For a shovel, maybe it'd go into a "miners' kit" that includes a shovel, pickax, and other earthmoving tools. If a party has the kit, they can dig x dimensions in y time on all but solid stone (or something). If they don't, maybe its x/4 dimensions or y*4 time (or both), or maybe they can only dig in loose soil or something. And do the same thing with camping gear, survival gear, etc.
At the end of the day, if you've got 'x' kit, your party can enjoy 'y' benefit.
It cuts down on fiddliness in the character sheets and asinine arguments with the DM over stuff like how wet or stony the ground is. And it's fundamentally more realistic in the fiction too. Unless your characters are morons in the setting, they would know what kinds of stuff they'd need for a camping trip or an excavation or whatever else a helluva lot better rhan the players or the DM would.
But that's me personally.
In either case, I expect that if a piece (or kit) of equipment is going to be adventure-relevant, then the rules should somehow describe what PCs should expect out of them.