There isn't a relatively simple explanation, I'm afraid. As you've pointed out, there are more exceptions-to-rules than than there are rules; however, there are some general guidelines that might help you:

• before double consonants

  before double consonants, 'i' is usually short regardless of its position in a word: as in bitten, hidden, miffed, bigger, piggy, ribbon, nibble, chill, pillow, immune, simmer, dinner, innocent, snippet, hippo, irregular, irrelevant, miss, bliss, issue etc (the only exception I can think of is 'dissect' which can be pronounced either with a short 'i' or long)

• in prefixes

  'i' in common prefixes such as in- (im-, il-, ir-), infra-, inter-, intra-, hemi-, dis- etc is pronounced short (exc. bi- and di-)

• before the suffix -tion

  before the suffix -tion (in simple words, ition words), it's almost always short as in competition, condition, inhibition, exhibition, recognition, transition, addition etc

• in ity and ible

  in ity and ible, it's usually short (either /ɪ/ or /ə/) as in ability, activity, elasticity, sexuality, visible, edible, eligible, tangible, divisible etc but there may be exceptions

• in the suffix -ise/-ize

  the 'i' in the suffix -ise/-ize is almost always long as in realise, actualise, mesmerise, hypnotise, formalise, italicise, memorise etc. Also, as @rjpond pointed out in a comment: "Expertise" is a relatively recent borrowing from French ("machine" is also from French) so the "i" is /i:/ (which isn't short, but isn't diphthongised either).

• in ic and ical words

  before ic and ical, 'i' is almost always short as in classic, lunatic, logic, ironic, fanatic, genetic, classical, historical, physical, mechanical, etc

• before digraphs

  a digraph is 'a combination of two letters representing one sound' (Lexico). For example, the ck in 'back' or the ph in 'physics' or the ng in 'ring'. Before consonant digraphs (and consonant trigraphs), 'i' is usually short as in stick, brick, ring, king, fish, lavish, ridge, bridge rich, sandwich, witch, pitch etc

• in -ing

  in the inflectional suffix -ing, 'i' is almost always short as in making, raining, killing, selling, feeling, hiding, watering, hitting, sitting, calling etc

• words ending in ign

  words ending in ign usually have the long 'i' sound as in sign, consign, malign, design, resign, align, assign, benign etc.

• before gh words

  before gh, 'i' is usually pronounced long 'i' as in sight, fight, might, high, sigh, height, slight, night, bright, right etc (ex. 'weight' which is pronounced with /eɪ/)

• before nd and ld

  before nd and ld, 'i' is sometimes long as in wind (v.), kind, blind, mind, mild, child, find etc (for w[ɪ]nd vs w[aɪ]nd, read this answer)

• before silent e

  words ending in iCe ('i' being letter 'i', 'C' another consonant, 'e' the silent e) are usually, not always, pronounced with a long 'i' as in hide, site, kite, white, wife, oblige, like, spike, bike, file, tile, while, time, prime, line, fine, pipe, gripe, size etc. Exceptions: recipe, clandestine, astatine and routine (long 'e': /iː/), urine (can also be pronounced with long 'i'), iodine (it can also be pronounced with long i), ive-words below etc

• words ending in ive

  ive words are tricky. Most words having the prefix -ive have short 'i': relative, conservative, fricative, figurative, active, argumentative etc. By contrast, live (adj), dive, drive, five, revive, alive etc are pronounced with a long 'i'

• CiC words

  words in which 'i' is flanked by two other consonants is usually pronounced short as in signal, signature, sit, fit, kit, hit, lit, spit etc (ex. title, vital)

There are also other exceptions such as:

• finite - infinite, migrant - immigrant, divine - divinity
• It's pronunciation varies when it occurs in combination with another vowel.
• Before rC (r + another consonant) it's usually /ɜː/ in British English and /ɝ/ in American English: bird, skirt, shirt, dirt, firm, irk, quirk etc

There are no hard and fast rules. Sorry.

(Long 'i' is /aɪ/ as in bite, short 'i' is /ɪ/ as in bit.)

Sure...

https://youtu.be/6aE-nMS9Mnk?t=28

The part where it says "...that I could be kind of human..." he pronounces it as /I/
Right?

I'll elaborate a bit on Barrie's point, which is correct, if disappointing.

The problem is that English spelling was not designed for Modern English. It was designed for Middle English, a very different language. When Middle English changed its pronunciation to become Modern English, English spelling did not change. Furthermore, English borrowed many thousands of words from other languages, which were of course pronounced differently, and spelled differently still.

The result is that one has to choose between two strategies in learning English words, however they are spelled -- this is not a problem confined to the letter I -- or else figure out some way to mix them.

Either you can actually learn the historical rules about pronunciation and learn to distinguish the different kinds of word each rule applies to -- which amounts to learning some basic linguistics,

Or you can do as Barrie suggested, and memorize 2 things about every word you learn -- (1) how it's spelled and (2) how it's pronounced (Kenyon and Knott is your friend here) -- and just ignore the possible but treacherous correspondences you might suspect between Middle English or foreign spellings and Modern English pronunciations.

The second option amounts to giving up all hope of making sense of English spelling. Most native English speakers do this, which is simpler for them, since they already know the pronunciation.

Since Anglophone education systems don't teach anything about English language, they never learn any different, and many still believe there should be a simple rule for pronouncing every letter.