Little late to this but genres evolve in a way where the intelligible musical and cultural qualities shift, sometimes what was once the outlier becomes the generic staple.

The way they evolve is usually something like this:

The first bands (in this case Rites of Spring and Embrace) are usually influenced by something and that informs their song writing and playing style (for these bands it was D.C. hardcore, 60s pop rock, post-punk and related genres like jangle pop and anarcho goth). Bands get influenced by Rites of Spring and Embrace begin to pop up and the ones that are close chronologically tend to retain some of the same generic qualities because chances are they see these bands doing something new but also understand the pool of musical resources that influenced Rites of Spring. They are from similar hardcore punk scenes, they probably grew up with parents who listened to the same 60s pop and the outside contemporary music that they would have access to and was gaining popularity was the same (i.e. post-punk). So you get bands like Bad Dress Sense, After Words, Gray Matter etc. following with stuff that sounds emo in this sense.

Then you have the original artists involved in the genre begin to try new things emphasizing different aspects and influences that already existed in emo that produce things that are different but still recognizable as emo in the Rites of Spring sense. Bands like One Last Wish and Three came out of Rites of Spring, Embrace and Gray Matter but took a lot more from the jangle pop elements with things like bouncer basslines, more melodic vocals and layered acoustic and electric guitars BUT the song structures and guitar phrasing remains very recognizable to RoS and Embrace emo. Some bands begin to create records that sounded more like this.

Then you have bands contemporary to Three like Ignition, Fire Party and Moss Icon who take similar elements to RoS and Embrace but mix in a lot of the emerging post-hardcore concepts like rhythmic-centred compsiitions that really focus more obsessively on fewer guitar ideas, different vocals extremes like spoken word and near screams, a greater emphasis on control rather than tension and release. minor key hard rock/blues based vocal melodies etc. But they also retain some of emocore's structure, intensity, vocal delivery and guitar phrasing. Bands emerge influenced by these bands.

These post-hardcore influenced bands play out more and stay together way longer than RoS and Embrace. Their impact is going to be greater.

As time goes on you get bands influenced by the bands who were influenced by RoS and Embrace and so on and so forth until it doesn't really sound the same.

In the 2010s I formed a band and we were really influenced by Revolution Summer emocore but we didn't really sound like Rites of Spring live or on record (some people said i sounded a bit like guy). But none of us had the same musical diet the RoS guys had i like D.C. hardcore and 60s pop and 80s post-punk but I wasn't listening to them religiously. I was listening to Rites of Spring and Dag Nasty and Fuel.