There are times for things to be different than they used to be. The same thing applies even to languages. Some are at a fast pace, while others like Lithuanian are the slowest. There is something called archaism, which apparently was a thing for the Central Thirēan languages if you looked at Biblaridion's conlang showcase videos. Regardless, no natural languages are immune to change. This could be applied to naturalistic conlangs via simulation of sound evolution, and grammar evolution.
Let's stick with sound changes for now. Remember that this applies to all instances of a particular sound going through a difference in a described environment across the languages in all areas. No attention is ever paid to grammar. Languages with similar or the exact same phonology can change to sound completely different from each other regarding the occurring sound changes and the distribution of their sounds. My advice is to figure out which sound changes are most likely to occur first and order them properly unless specific changes are equally likely. Maybe the grammar changes could help with that, but they're for the next chapter.
For our demo conlang, I'm thinking of the evolved edition, prior to the four dialects splitting off as their own languages, utilizing, alongside plain consonants, lateral released consonants, and pharyngealized ones. Everyone knows about pharyngealized consonants, a common feature of Semitic languages, especially Arabic. Lateral-released consonants, to be, might be abhorrently underrated. One language I discovered a lateralized [tˡ] was Navajo. Recently, I looked at the phonology of the Hmong language and discovered its richness of lateralized consonants and prenasalized ones.
I want to include some sounds, like the palatal lateral and nasal, to see how far I could take palatalization compared to others. And instead of postalveolar fricatives and affricates, I'll go for the alveolo-palatal ones, to give the modern language extra flair. But which sounds to get rid of...
And what of the (C)V syllable structure and the stress system... Perhaps I could introduce consonant clusters. Maybe not. Actually, I might need to allow clusters by dropping vowels so that I could create lateralized and pharyngealized consonants.
This is where you come in. Look at my chosen grammatical features, and my collection of words, then figure out the order of sound changes for my desired goals, any extra sounds worth including, and which proto-lang sounds might be absent in the modern lang. As this is Wattpad, paragraphs can be annotated, and comments could be left behind like on YouTube and other social media platforms, which Wattpad apparently classifies as. So if you got ideas, tell me. I'd like to hear them. I might select the order and the results, and see what order would best suffice. Maybe some grammar changes as well.
Perhaps Kayinth might possess some ideas.
To clarify, I'm new to applying sound changes, so I oughta seek out help from the right people, including whoever is reading this.
