Rom 11:17, rendered correctly, is a key for understanding Romans, and especially Romans 9–11. But of course this ‘verse’ (Paul never wrote a single verse—they were created much later) is a part of the whole. A letter like Romans truly is as fabric, with a warp of ideas and thoughts, and then the weft, containing a range of different things. Partly they can be un-connected, but often they are connected. I think this has to do with ‘writing psychology’, I think.
Paul very early betrays that the role of the Jews is essential to the letter: 1:16–7 “to the Jews first, then to the Greek.” This is mentioned several times in the earlier part of the letter, perhaps a bit puzzling. In any case it becomes clear in chs. 9–11, where Paul in one of his more complete commentaries on an issue, discusses the relationship between Jews and gentiles at length. It it advisable to read it as a whole. Then it becomes clear that Paul’s problem is how to win the individual Jews for the faith that Jesus is the Christ. He early (9:1–5) states that “theirs are the covenants”, which probably means the old as well as the new. Anyway it is clear from these verses that Paul acknowledges the position of Israel as God’s peculiar people. The concern of Paul throughout the discussion how Jews realte to Jesus, but this never results in the idea that Israel is no longer this peculiar people. Rather, Paul envisions a final coming in of all Israel.
This (VERY briefly) said as a background to what I wrote about Rom 11:17. Thus Romans 11:17 in its correct rendering is quite in line with the rest of the letter.