I know that this is a potentially broad subject but there seems to be a phenomenon where later generations of scholars (i.e. after the close of the Gemara; the Amoraim) come up with new halakhoth or restrictions based on either questions or safeqoth that were never considered or taken into account before.
For instance, the berakhah of shelo ^asani goy was said by all Jews - native-born and convert alike - until some scholars among the Rishonim began to be medayeq on the literal wording of the berakhah and decided that converts should not say it - and even began inventing alternate berakhoth! These forms of the blessing had never been heard of before, or even seen as necessary, by any scholar of any previous generation; not the Tannaim, not the Amoraim, not the Geonim.
This type of thing arises in numerous instances and no one seems to ask in response why, if the halakhah was 'good enough' for the earlier scholars/authorities, it needs to be changed or altered.
My question is: Is this type of innovation warranted, necessary, or even possible? Shouldn't the halakhah remain unless changed by either reality or an authorized beth din [ha-gadhol]?