If “The Church” were only made up of its believers you would have a point.
But The Church is not ‘only’ made up of its believers.
The Church–being the Bride of Christ–is thus in a union with Christ.
CHRIST is thus not just ‘in’ the Church–He, united to His followers–IS the Church.
Therefore–and Lord knows you not only have seen the relevant teaching on this and other threads, including the citations of documents and links to the catechism so you have no excuse whatsoever for your continual refusal to accept those teachings and substitute false ones which you then claim 'are what Catholics believe–The Church, according to Christ Himself who left the Paraclete to guide us to all Truth, established His One Church which is the Catholic Church, in matters of faith and morals as revealed to us by the Paraclete under circumstances clearly laid out, cannot teach error. The Church cannot, at one and the same time, BE Truth (having within itself Jesus Christ in union) and be “untruth” (teaching untruths).
Jesus never promised that His Church would be full of perfect people Quite the contrary. Jesus never promised that, in recorded time, people who belonged to the Church would not perform actions that later generations would find ‘wrong’ even if in the time they were performed they were considered not to be wrong. (We are of course speaking of matters specifically related to the transmission and teaching of doctrine/dogma. We are not speaking of secular and matters that are not involved in such teaching. Popes were, are, and will be capable of personal sin. They will be capable of making wrong judgments on matters outside of faith and morals. If you think otherwise, you have confused ‘infallibility’ with ‘impeccability.’) Never, ever, did Christ say, "and lo, the members of my church, yea, even the Vicar, will be incapable of personal sin and ye shall know they are my church for they will be the only church which has perfect people in it at all times.’ Because if you’re claiming that because Catholics aren’t perfect, they can’t be the True Church–guess what? You are then saying NO CHURCH IS THE TRUE CHURCH–because, of course, there is no church of perfect people–and you are then stating that Christ was a LIAR because, if there IS ‘no true Church’, and we KNOW that Christ promised to establish His Church and the gates of hell would not prevail against it–but, whoopsie, there is no ‘true church’ by YOUR OPINION–you have thus made Christ a liar. Whoopsie indeed.
The Church has never taught that what was taught ‘from the beginning’ as true can at any point become ‘not true’ when it comes as matters of faith and morals.
Since ‘geocentricity’ was never taught dogmatically, it obviously could have been believed (scientifically speaking, not 'theologically speaking, you are confusing the two if you think that because a person argued about ‘earth center of universe’ that it was purely, or even mainly, on theological grounds) at one time but not at another.
Since the Trinity was taught as truth from the beginning, though the fullness of the doctrine developed over time and we still do not fully understand the mystery, the Catholic Church maintains this teaching as ‘infallibly true’.
Interestingly enough, there are some Protestants who do NOT believe in the Trinity. They use all sorts of Scripture-alone to support their view. In their teaching though, they have maintained that what was taught ‘then’ was an error, and what is taught now is correct.
Likewise some (not all) Protestants teach the Eucharist is symbolic. This was not Christian teaching at the time they ‘developed/made up" the teaching. Christian teaching was, and had been since the time of the apostles, that the Eucharist was really and truly the Body and Blood, Soul and Divinity of Jesus Christ, re-presented (not resacrificed) at every Mass. These Protestants, refusing to accept anything but their own, ‘personal interpretation’ of Scripture, changed Christian teaching on the Eucharist such that what ‘had been’ taught ‘before’ was absolutely not what was taught’ now.
So which church(es) have been tinkering with doctrine and changing it? If you say the Catholic Church does so, show the doctrine that it has explicitly ‘changed’ . It should be easy. There should be a Papal Bull or a document which says that "from now on, Catholics will no longer profess in the Trinity. . .or the Eucharist. . .or Purgatory. . .or have ‘male only’ priests. . . or decided that contraception is okay, and abortion is permitted. . .