The Oort Cloud *may* exist, it was theorized in order to solve some problems. The TNOs are intermediate between the outer Solar system and the KBOs. The Kuiper belt probably does exist. If either has been there throughout the 4.5 billion years of the Solar system, that would make a large reservoir of past and future comets, inner system asteroids, and impactors.
Yes and I also think TNO’s KBO’s and OCO’s (If I may invent that acronym) aren’t all we think they are, since we know very little about them.