RabbiofBerlin: hair-covering is technically required by halacha, and is not just a chumra. However, it is a special case, since many Orthodox communities historically and today don’t practice it. For that reason, as mentioned on a thread in which this issue was discussed extensively, some rabbis have expressed the intention that a failure to cover one’s hair (in a community where this is uncommon) does not indicate a lack of acceptance of the mitzvas.
More generally, I think you’re right that increasing stringencies are a problem. It makes it harder to argue convincingly to the non-frum that Orthodox Judaism is the only valid form of Judaism, because they see all the recent stringencies and mistakenly conclude that Orthodoxy is something new and extreme, rather than the continuation of traditional Judaism.
There needs to be moderation and balance in halacha: Devarim 4:2 says not only can we not subtract from the mitzvos (as the heterodox do), but we can’t add to them either. It’s a good thing Orthodoxy has many varieties and is not controlled by a single hierarchy or pope. This way moderates and even lenient authorities (even people like R’ Abadi on Kashrus issues) can have a following and influence.