Redemption Then Prayer

We know that there is a halacha in the gemara that we must be סומך גאולה לתפילה at maariv [and shachris]. After ברוך אתה ה' גאל ישראל we say השכיבנו - that according to the gemara is an "extended geulah" and thus not a hefsek. My son asked me how is it permitted to say kaddish before shmoneh esrei which is NOT mentioned in the gemara and is a later takkanas hagaonim? We are losing out on our סמיכות גאולה לתפילה??