[leeoniya]

it's really only nuanced when you have small team and a very tightly scoped project.

for anything that can plausibly grow in scope and team size (which, let's be honest here, is most complex projects), it almost never makes sense to go without an existing ecosystem. it becomes difficult to hire, difficult to train, difficult to pass off maintenance, slows down velocity of shipping, makes your team gradually re-invent a worse version of the framework/tooling you initially tried to avoid, etc.

i've been on both kinds of projects. when i build something solo it's a work of art in code size, API consistency, and performance...and that feels truly amazing. but unfortunately it's not something that is feasible with bigger and more diverse-skillset teams. ever-growing scope and shipping features quickly usually means giving up performance and well thought out design.