Actually it was 14 BP. And it only had 85% accuracy... Gen 1 move design can be bizarre at times.
Going by Gen 5 alone, it is resisted by Steel which is the same with Dragon making it a point towards coverage, Dark which is only really relevant for Tyranitar as Hydreigon is Dragon type and Weavile is an Ice type, and Psychic where Gen 5 OU has 9 properly in the tier and another 9 with some degree of viability. It does look from that that coverage is more likely than Psychic being too weak. Also it kinda weakens your argument a bit when one of the reasons you say a type is so weak is due to the fact a sizable portion of the tier has it.
Also there are three pure psychic types in Gen 5 OU, and you left out Espeon. Granted, I think that it's a Electrivire situation after they dealt with Baton Pass, but it's still there.
First of all, Tyranitar in Gens 3, 4 and 5 may be one of the best Pokemon of all-time. Put more respect on my goat's fucking name. Secondly, Psychic types that used Psychic moves were because they were monotype (like Alakazam).
Psychic-Types in Gen 5 OU are essentially like this:
Alakazam and Reuniclus derive their viability primarily from their ability, which is really controversial. Alakazam being the offensive one, Reuniclus being a great wall. Both get their viability from ignoring hazards, and both are majorly weakened by Pursuit. Alakazam having to run Focus Blast makes it way less consistent, and many have tried to get around that to varying success (usually little).
Latios basically ignores the Psychic STAB with Draco and Surf as primary attacking moves. Using Psychic likely just gets it killed as Tyranitar switches in already to Pursuit it, of which a lot of Latios as is get a lot of their value from chunking Tyranitar for the Rain team it's on to try and get the kill back, or hope Latios finishes it. Latios. The Psychic Type only adds one meaningful thing defensively, which is making it a good answer to Keldeo when things get dire, but the teams it's on are usually packing something like Tentacruel anyways.
Celebi was popular until it wasn't If the generation continued, it'd almost certainly not be in OU. Celebi had 6 total appearances in the course of SPL XIV Gen 5 OU, which is not that good.
Jirachi derives its value from being Jirachi, a Steel-Type which means it resists all of Psychic's weaknesses. Which is not good balance, either. Jirachi also does not use Psychic moves because it's a pretty bad typing, and instead its role is that of a Variety Monkey, packing utilities an resisting Latios (not Latios's Psychic, because that doesn't exist, for clarity!). Even when Jirachi uses a Calm Mind set, it basically never packs a Psychic move, instead sporting better coverage such as BoltBeam. Psychic only helps it quad resists Psychic (which who cares), be neutral to Ghost and Dark instead of resisting it, and be neutral to Fighting which is useful, but overall even at the best dualtype possible for Psychic in Gen 5, it's really not doing that much for its partner type.
Lastly, Starmie, and you're not gonna guess it: It doesn't use Psychic. This time though I will say Starmie being a Psychic type is valuable defensively, more than Latios because Starmie sets can be more utility focused which is better than still unrecoverably losing like 40% with rocks to a Keldeo. That is something you generally want to avoid, Latios is an emergency check. Starmie has sets that are pretty offensive still, don't get me wrong, but it's also a much more versatile mon that can get free turns versus other rain. Outside of that though, yeah, Psychic is just whatever.
Overall I'd say Gen 5 getting so many Psychic types is primarily due to Keldeo but also in general just 2 of them having good stats and Magic Bounce.
And I don't know why it's so hard to understand, but I want Psychic Type to be a good type in a vacuum. Not just "if it has this ability, and this great stat spread, and if it has a good dual type." I want it to be a type that has more defensive or offensive utility meaning that you actually want to proactively fit one onto your team, rather than it more being a drawback to an otherwise amazing Pokemon. Because in most gens, that is what Psychic is: A detriment to the Pokemon it's on. Especially due to Pursuit, but even now it's hard to get anything going with a Psychic type before Ghost Types (Which are literally better offensively and defensively, both sharing the trait of being a special type that generally can hit almost anything neutrally besides the key types, but Ghost is neutral against Steel), Knock Off, U-Turn, etc.
This isn't too much to ask as many tiers have this, especially when you look at lower tiers. If you look at images of the top Pokemon in every tier, you will always see certain traits and qualities in Pokemon (such as types) get to the top. I don't need Psychics to be a top 5 type or something, but I want it to have an actual purpose besides just being there to be owned by the several types that own it.