Level 1s rarely decide the game, especially as Aphelios. For extended fights, Conqueror will do.

The only ability that is an auto reset is Moonshot/Calibrum marks in general, but they're not very effective as auto resets except with a very specific niche mechanic, because of the reset being gated by when the mark lands on someone rather than when you press Q, as most other auto resets work.

Every other ability that could be considered to function as somewhat of an auto reset ( Duskwave, Moonlight Vigil) just doesn't provide Lethal Tempo stacks because of weird coding.

Also, calling Aphelios an auto-attack champion is a bit misleading when compared to something like Jinx, because while its true that their auto DPS is comparable (Aphelios actually does notably more once scaled), Aphelios will kill in 3 autos a champion that Jinx will kill in 7 autos; his DPS is heavily loaded into the power of each individual auto because of the 26 AD and 27 lethality. With lategame Onslaught, you can even kill a whole champion with just a Q press. If you're only getting 3 Lethal Tempo stacks in the time it takes you to kill 1-2 champions, then your Lethal Tempo is basically doing nothing.

And aside from that, while it's true that Aphelios is very auto reliant still, what's often overlooked is that he's also a bursty spellcaster on top of it; it's just as troll to not play around his abilities as it is to not play around his autos. And he bursts so hard that he literally just kills people too fast for Lethal Tempo to do anything in many cases. In the average fight, he will throw significantly less autos than the average Lethal Tempo ADC, even though he out-DPSes them. There is no time to waste on a keystone like Lethal Tempo when you can literally kill a whole champion without getting a single stack. You want keystones like Press the Attack or Conqueror (or Fleet Footwork if it wasn't so nerfed) where it plays to both strengths; enhancing his autos and his spell casting.

I'm not saying that there aren't scenarios where Lethal Tempo doesn't outshine other options, particularly in very long fights or level 1 fights. But those scenarios are usually outnumbered by all the other scenarios you'll encounter in any given game where it just underperforms.

I won't discount the fact that in very very high Elo games (and possibly in regions with unusually aggressive early playstyles like China) there may be a viable niche for Lethal Tempo, if you can confidently expect the game to be heavily decided within the first few levels.

But for most players, the game is rarely over by 3 minutes, and Lethal Tempo will rarely be the decider if it is, meaning I would advise people to not even bother thinking about when you might want to run it. It's not a good return on effort invested trying to find the 1 in 100+ games where it will actually be optimal just for it to be only slightly better still.

The runes section goes very in-depth into discussing PTA vs Conqueror vs Lethal Tempo, I recommend giving that a read!

I don't buy Kraken Slayer anymore, the screenshot of me buying Kraken Slayer every game is from back when it gave crit.

LDR always does more straight up damage than Collector at second item. Its main weakness used to be buildpath, which since it started to build out of Noonquiver is no longer as much of a concern.

You can still do Collector second for snowballing (securing kills and getting extra gold from those kills) if it doesn't seem they're going to build armor soon, since the damage difference isn't yet as high as it will be, but any armor like Tabis is already enough to push LDR into being much better than Collector. I usually find myself building it second these days, and Collector third.

I don't have much experience with playing Aphelios mid, but typically ADC mids need mobility to have a chance at being stronger than on bot lane, immobile ADCs like Aphelios struggle more in the mid lane ecosystem and trying to survive ganks without vision/peel from their support. He is viable though, just not as good as bot lane. But he's viable so you can play it if you just really prefer that lane. Just make sure you always run Barrier, even before its buff solo lane ADCs have always performed significantly better with Barrier than with any other summoner spell according to stats, they likely scale better with its survivability than other picks do.