A level 1 PC who has spent a very limited resource (a feat) and has spent a couple of somewhat limited resources (proficiencies and ability scores). And this is "no way"?
Right. "Hard" is supposed to be hard. Now, an active check makes Hard not so hard for such a player, but for a passive I'm-not-totally-paying-attention check, yes, Hard should not be trivial.
I said how I would do it: 5 + prof + mod for normal passive perception, -5 for disadvantage, +5 for advantage. Now, if the players are *actively* doing something repetitively, I would either do the standard passive perception, or I would still have them roll once for each general area to see how successful they are being on average at the time.
Rolling every 5 feet is ridiculous. But roll once per minutes/10 minutes/hour of travel is fine. Have them roll for groups of things.
Take a scenario of a character (WIS\Perception +0) and a tunnel full of 50 moderate-difficulty-to-spot traps. Without rolling any dice, how would you determine which traps, if any, the character spots as they alertly walk along the tunnel?
This character's passive perception is 5 + 0 + 0 = 5. He would spot Very-Easy-to-see traps automatically. If he is actively looking for traps rather than enjoying conversation with his party members, his average active perception would be 10 + 0 + 0 = 10. Moderate difficulty traps have a DC of 15.
If you went straight PP against DC, he wouldn't see any of them.
For active perception, in actual rolling, no modifiers, you beat DC 15 6 out of 20 rolls, which is 6 * .05 = .3 = 30%. So, you could say he sees 30% of the 50 traps: 15 traps.
You can calculate this as (21 - DC + skill mod) * 5%.
For not-looking-for-it passive perception, it would be 5 less: (16 - DC + skill mod) * 5% = 1 * 5% = 2 out of 50 traps.
Or, more fun, if he is actively perceiving, you can have him roll twice, one for the first group of 25 traps, and one for the second group of 25 traps. Or 5 times and split them into groups of 10: whatever fits the design of the dungeon/area better. If he is not actively perceiving, have him roll with disadvantage.
In contrast, a 5th-level Observant, proficient, +4 Wisdom character would have a passive skill modifier of +12 and an active skill modifier of +7.
Inactive passive: (16 - DC 15 + 12) * 5% = 13 * 5% = 65% = 32 of 50 traps.
Active average: (21 - DC 15 + 7 ) * 5% = 13 * 5% = 65% = 32 of 50 traps.
The Observant player does not gain a benefit to active perception (I am continually looking for traps!) but only to passive. This makes his passive (inactive) perception just as good as his average active perception.
If passive perception stays at 10 + skill mod, an Observant player will actually be 25% better at seeing things when he is not looking for them than when he is!