Just a nitpick, but I’m like 100% certain you’d be able to hear the difference between Bach and Beethoven lol

Even going further back to the 8-bit era where there were way fewer sounds to play with, the limitations of the hardware meant the composers had to be super efficient with their writing in order to wring the most out of (on GB(C) and NES) two pulse channels, a wave channel, and a noise channel. Of course, it's not that every OST from this era is good, but the ones that are have lasted so long because they have strong, memorable melodies. So even if you take compositions these and make them orchestral (as in the original Pokémon anime OST), their essence still shines through. I mean hell, you look at tunes like Ronald's Theme or the Grass & Lightning Club Themes from Pokémon TCG and they don't feel like they're missing anything (was really pleased to see 8-Bit Music Theory's video on that particular soundtrack do well, more people need to hear it!)

That's not to say that the only valid form of composition is a melodic approach, but there's a reason why I can still whistle the melodies from Pokemon Gold/Silver/Crystal even only having played them once and only occasionally listened to the soundtrack in the decades since, yet even 150 hours into Elden Ring and counting I could not sing you a single bar from any piece in the score if my life depended on it (admittedly, for a game like Elden Ring, singable melodies might not fit the vibe).

The upshot is that there's nothing stopping composers from taking this approach when writing for larger ensembles; examples include Gusty Garden Galaxy and Rosalina in the Observatory from Super Mario Galaxy or the main theme and Revali's Theme from Breath of the Wild.

You'll have to forgive me for only using Nintendo examples--that's just what I've played a lot of, so it just ended up that way. Another excellent example of melodic writing is the Undertale OST, where Toby Fox channeled that style of writing to perfection.