Nothing wrong in not wanting to use alcohol or limiting alcohol in your cooking. Also your question was about Tiramisu, which if you go with the authentic version uses wine in it's preparation not rum. Now there are many many spins on the classic recipe and there is no reason you can add your own spin to still get a fabulous outcome.
Use strong dark coffee and not coffee liquor if a recipe calls for it
I even use cream cheese and heavy cream in place of the more expensive mascarpone if I don't have it handy
Use fresh vanilla bean (slit lenghtwise and remove the soft inside bits of it in the cream). Vanilla beans are expensive but certainly available at many ethnic stores or high end stores like sur la table, williams of sonoma or you can buy them online.
Use zest of an orange or lemon for additional flavor
You don't need to use any alcohol or even extracts if you don't want to.
I have cooked many things that call for wine (which again I don't use due to the alcohol content). At times if I have a non-alcoholic version of it available (in IL where I live, most grocery stores sell this) I will buy it and use it or I just use water, stock, lime or lemon juice or grape juice as a substitute. It works just fine for me.
Again I am not too bothered about other people's perspective on my lifestyle, I just do what makes me comfortable and keeping alcohol out of my house is one of those things. Cooking is such a creative thing, the fun is in trying to try different things and never follow something to the T.
All the best.