But, yes, 5e is less deadly than, for example, 1e. Some people really enjoy it, others not as much. If you don't like the rules on resting, there is a simple solution available to you- change the rules. There are numerous semi-official (DMs Guide) and unofficial variants for resting and healing you can use. Use them!
Funny thing, since I continue to go through the older books regularly, 5e is more deadly than 1e when it comes to dying.
In 1e, when you reached 0 hp, you had 9 rounds before you died (those are 1 minute rounds). An "optional" rule (really a sentence) says you could be knocked down to as low as -3. That's still 6 rounds before you die.
Now, you didn't get death saves. Each round you lost 1 hit point. But all that had to happen was another player had to spend a round tending to your wounds. No healer's kit. No skill check. Automatically stabilized at 0 hit points.
BUT - you were in a coma for 10 to 60 minutes, and then all you could do was move slowly for a minimum of a full week. Even with healing potions or magic short of a
heal spell, you were out of commission for a full week.
What was more deadly were things like poison, which were usually save or die.
In response to the original post:
I have changed the rules on resting and short rest/long rest abilities and the like for slightly different reasons, but it resolves any of these types of problems too.
But until then, the the primary solution was simple for us:
The characters are people, and we treated them as such. We didn't treat them as pawns in a game. They have goals, regular lives, and their habits. It was essentially an agreement that they would treat the day as a day. And they would rest at appropriate times. Part of it was simply that we didn't want the rules to change the way our characters acted from before we switched to 5e.
Another fun fact - AD&D
required rests. "A party should be required to rest at least one turn in six (remember, the average party packs a lot of equipment), and, in addition, they should rest for a turn after every time they engage in combat or any other strenuous activities. (Remember that a turn is 10 minutes.)
It mentions that wandering monsters are possible, but "may be moderated somewhat, depending on conditions" and "Too frequent interruptions may make spell recovery impossible."
So there were no actual consequences for not resting, but guidelines for the DM to give them a break when they did rest.
I do agree that "adding time restraints" is not a good answer. Nor am I a fan of punitive random encounters. The easiest rules fix is that you can only benefit a long rest once/day (as noted), and you can only benefit from a short rest every 4 or 6 hours (two per day, or whatever number is appropriate for your campaign). To me it has nothing to do with the number of encounters.
That's the rule side of the equation. The rest of the equation is the players agreeing not to think in terms of game mechanics and get on with the adventure. We expect that they'll take at least a few minutes break after a combat, they'll stop for lunch, and probably an afternoon breather, before stopping for dinner and to set up camp for the night. We expect that the pattern for a daily life will remain the same as usual.
In other words, focus on the characters and their actions in the game world, and don't worry about the inconsistency that the rules make. If they bother you enough, though, you'll have to change them. Either by using one of the alternatives in the DMG, or the many home-brews or your own design.