I think both you and Breakdown can be correct. TLJ could work as both a trilogy ending (provided there was a continuation to it), but it can also work under the premise that the plot threads it does set up could be resolved in the following film.
One thing I don't see people discussing much is that Rise undercuts the ending of TLJ, in regards to how people, ahem, "rise" against the First Order/Final Order. In TLJ, there's the reveal that Luke's actions on Crait have inspired people across the galaxy, so what I took from that is that it would lead to an upswell of resistance against the First Order. Instead, the people get on the good guys' side because Lando goes to the core systems and rallies the people. It negates Luke's sacrifice, and undercuts a theme from TLJ - that there's strength in the hero myth, that people need heroes, even if the hero themself isn't perfect. Rise's view is that all you need is a pretty speech.
Which is arguably a shame, because one of the best lines in the film IMO is when the First Order says "they're [the attackers against Exogol] just people." It simultaniously ties in with TLJ's themes, while also casting them aside.