Past Simple with signal words describing frequency in the past
Primarily for habitual actions:
She usually went to the movies across the street
They sometimes showed a good movie
We can use other means to show that an action happened regularly, however, this is a completely different course (used to / would).
Past Simple and Present Perfect with signal words describing marginal frequencies
The marginal frequency is either “never” or “always“. Indeed, marginally (utterly) seldom is never. Marginally (utterly) frequently is always.
Watch out if you use the words describing marginal frequencies like always or never, we can use Present Perfect here, of course when there are no indicators of time at all (yesterday, today, at 5 etc.):
I have always liked him (and the speaker likes him now)
I always liked him (it is not clear if the speaker likes him now)
Pete has never done that (up until now)
Pete never did that. (it is not clear if he did that or not after that period of time)
In a nutshell:
Signal words like usually, sometimes, often, and rarely, many teachers explain them as signal words for Present Simple. That is why students are confused. We can use these words with Past Simple and in other tenses and constructions.
Also on Past Simple: