So I've thought about how to express a reply to this. There's a few different issues: the issue of pre-written prayer, that of prayer books, a general issue of superstition, and the specific issue of beads/etc.
I'm not against pre-written prayers. Scripture has over 100 available (the Lord's Prayer and the Psalms). The catechisms all give instructions on how to use the Lord's Prayer (and by extension, any pre-written prayer) as a pattern for prayer. So as you gain familiarity with the written prayer, you understand it and can pray it genuinely by including mentally (or vocally, if alone) the particular items that fit in the general petition of the prayer.
The prayer of confession in the BCP is a good example of a pedagogical aid. It is general and comprehensive, so it works as a pattern. Once you learn it, you can augment it (vocally, or mentally if it is public prayer) with specific items to confess. Keep in mind that the purpose is pedagogical: to help you learn how to pray, not to dictate or constrain your prayer (it should be like scaffolding). In my experience (anecdotal: from observations and discussion), very few people I know that use prayer books use them this way. Instead, they either pick new pre-written prayers (never learning, thus never understanding), or rely on the pre-written words without augmenting them with substance (so they only have scaffolding). Also, because of the abundance of prayers in the prayer book, they tend to ignore what Scripture provides, and to ignore the catechism's instructions for prayer. So what Scripture provides (the Psalms) is displaced by a substitute (the prayer book) because it purports to perform the same function. While pre-written prayers can help provide structure and teach how to pray, I find that in experience (again, anecdotal) prayer books tend to be unhelpful.
This leads to the superstition point. I hear the excuse often (I have a friend really into "high church" stuff): "it isn't necessarily superstitious, it can be helpful for a legitimate end." And I grant: there is no logical necessity. Yet as fallen humans, we rarely exhibit perfectly logical behavior. Instead, reality overrules theory. And what we see from experience in reality is: the practice originated in superstition, it is used superstitiously by many, and it encourages superstition. Even those on their guard against superstition frequently fall into superstition. So any practice like that, which is not needed/commanded...I tend to doubt the "helpful" claim, and avoid.
Related: what I brought up before about the matter of displacement. Too often, the proposed "helpful" practice is unnecessary in that the purpose is either already accomplished, or able to be accomplished without the risk of superstition/ritual. My workplace proposes new policies all the time. I typically ask: "what problem is this trying to solve?" Then we have to check if it is already solved, or not a real problem. Frequently: the new policy is not necessary, because the problem has been solved (or is a made-up problem). Any "aid" to worship is intrinsically unnecessary if we affirm the RPW, that what God has provided for worship (in terms of activities/practices) is sufficient. So if the proposed help is adding an activity...then it is either a made-up problem, or it is for an end that God's worship already accounts for. That's poorly expressed, but the general idea is to ask the question of why we think it is needed/useful, and then see if that purpose is either 1) made-up, or 2) already taken care of. For example: remembering what to pray for - there is no requirement to close your eyes during prayer, and there is no requirement to pray without preparation. So it is perfectly fine to prepare a list, prepare the list with biblical help, and then to have the list on hand while you pray.
Beads: it originated in superstition, it is used superstitiously, and it encourages superstition. It is unnecessary, and the purpose (if it is for structure/memory) is easily taken care of without them, or any other practice that encourages superstition. The Roman usage is just for counting repetitions (which we are explicitly warned against in Scripture). Any Protestant versions of them are very recent and derived from questionable sources (the Lutheran one from a pagan source, the Anglican one explicitly from Roman Catholic and EO sources). The Anglican one actually says that you repeat the cycle three times "allowing the repetition to become a sort of lullaby of love and praise that enables your mind to rest." That is quite problematic. Again, not only is vain repetition warned against, but Paul very clearly says that we should pray with understanding, not so that the mind "rests." The spirituality behind the bead usage is not Christian.
If you pray with understanding, you should not repeat because repetition does not increase understanding (think about the joke of explaining the joke by repeating the joke; if you don't get it, you still won't get it). If it is a simple, occasional, prayer of "there's a danger here, please protect me," then such a prayer cannot require a structural/pedagogical aid of standardized words that are repeated in every instance. So there's no need to adopt dangerous practices that encourage and tempt superstition like beads, repeated regular/timed prayers, uniform wording, etc.
