>>43973470It's worth pointing out that the GBA had a maxinum storage space of about 32MB (Mother 3 used it entirely) and Sonic Battle is only 4MB. Emerald is 16MB IIRC, they easily had the space to do way more with the GBA.
If gen3 romhacks look more like DS games and have so much content crammed in like having up to gen 7 pokemon or good graphics, that's why. GF didn't push the GBA to its full limit.