No actually if you save the image files you could be better off. You have full control over colour and image type. It's not a backward workflow at all. It's a proper workflow. Where placing PDFs is advantageous, it can also be a disadvantage in limiting your control over your work as regards colour options. 6 of 1 and half a dozen of another.
I'd really prefer to have proper image files in my document than just a PDF. Where if the file was laid out in PDF I would have no problem with using the PDF. But PDF is not an image format in itself. Saving to TIFF or JPEG or EPS may save you a lot of work in the future when it comes to some printing companies RIPs.
Whenever you are working on a file you have to think of who will be working on it next, or who you're sending it to. There is no accounting for being lazy and just placing down the way it came in to you. There's a word for that for people that just place in RAW word files into InDesign and think it's ok and don't proofread or check the styles. It's called "idiot setting". I'm not saying anyone here is an idiot it's just that sometimes you have to make sure the file is absolutely 100% correct after you are finished with it. Otherwise, down the line there will be complications.
Either placing the PDF or placing TIFFs and JPEGs is totally acceptable. It's just the extra step of saving the TIFF or JPEG can give you much more control over your workflow as regards colour options.