Karn, Legacy Reforged - striving for consistency

Background: I have medium MTG experience, almost all standard (on Arena). Very new to the EDH and to deck building in general. Playing in a pod with roughly pre-con levels of decks in. I'm aware that playing colorless is hamstringing myself, I know there are 1000 other decks I could pick up and have easy success with, but what can I say - I just think artifacts are neat.

What I'm working with: https://moxfield.com/decks/5e77HsQ7UkqteQeXDL3Kfw

This is my current deck, the 'Considering' section are all cards I have access to. I'm really looking for ways to make this work better with these cards I already own, but I'm obviously open to expanding my horizons (within a sensible budget - I'd love The One Ring... but you know)

It's a fairly unimaginative pile of artifacts, I'm sure there are hundreds of cards I've never even heard of that I could slot into this to make it better.

My biggest issue consistency in the first 4 or 5 turns. If I get a couple of good mana rocks and cheap artifacts on the board then I can drop Karn on turn 3 or 4, and often pop off with a huge board on turns 5 or 6. This maybe happens 25% of the time? The rest of the time it feels somewhat underwhelming. Like sure I'll eventually get Karn out and start generating lots of mana etc. but maybe significantly later.

I guess my most obvious win-con I'm playing for is [[Walking Ballista]] with infinite mana (from [[Basalt Monolith]] and [[Forsaken Monument]] for example - but I think I end up with a few ways of doing this) or any of the various infinite card draw combos with [[Sensei's Divining Top]] and [[Mystic Forge]] with mana cost reduction stuff out. I guess ramping into a huge board state is also a valid option with this deck sometimes too.

Ways to get to these combos more reliably would be nice (I guess I should bring [[Planar Bridge]] back in...)

One of the (probably obvious) things I notice, is games where I get good card draw engines up and running are almost always a good time. So tweaking things to get these up more consistently would be nice.

Cards I'm not 100% on:

[[The Endstone]]: Feels amazing playing a turn or two with that on the board, but I'm unsure if it's actually worth.

[[Wondrous Crucible]]: Nice fun RNG and again, feels amazing to resolve it and start churning out free threats from the yard, but not sure playing for RNG is a great plan (ward 2 is nice though).

[[Blinkmoth Urn]]: I guess this is my backup Karn if he's targeted too heavily and I can't keep him out? It's symmetric but I guess only slightly - most decks won't have anywhere near as many artifacts out as I will.

The creatures in general I'm not at all satisfied with. I have a handful of creatures that create tokens (as well as [[Retrofitter Foundry]]) to turn on [[Idol of Oblivion]], I feel like [[Big Mother Mouser]] should fit really well into this deck (it either becomes a huge threat or a pile of artifacts generating Karn mana), but I can't quite pick what I'd drop for it.

Other stuff:

I would love to get [[Horizon Stone]] as I often end turns floating a boatload of Karn mana with nothing to spend it on, but again - not sure if this is just a win-more option.

[[Nettlecyst]] and [[Adaptive Omnitool]] both also seem like reasonable wincons I could use - strap Karn up and make him unblock able as a 30/30 seems decent?

I would also love to get [[Dawnsire]] in, but that's just the Timmy in me really wants to pop creatures for 100 damage with my 20/20 spaceship.

Anyway, this is getting long - I'd love some advice/tips/tricks/criticism please, thank-you.