I think this is an example of "recency illusion," which you described very well as the situation where "increasing observation" is caused by "increasing awareness."
From one point of view, the past participle could be said to be disappearing. But there are a lot of caveats, and the process has been going on for much longer than any single person's lifetime.
Past tense and past participle forms have often influenced each other or substituted for each other in the history of English. It seems to be easy for this to happen because they both have similarities in meaning, and for regular ("weak") verbs they are identical. There is definitely an overall tendency towards simplification in this area, and it is not confined to any particular region. But this tendency does't always lead to the elimination of the old past participle form; for many verbs it seems the simple past form is more likely to be displaced.
For some verbs, the past participle has already been displaced by the past tense form in at least some varieties of Standard English. Examples are get (where the form got is commonly used as a past participle, although the precise conditions of its use are often complicated), and mow (where the past tense form mowed is commonly used for the past participle instead of mown).
But for other verbs, past tense and past participle are merged only in non-standard varieties.
It's possible that this general tendency, plus influence from non-standard varieties will eventually cause some verbs to have fewer forms in Standard English, but this is by no means inevitable. If it does occur it will be the end result of a centuries-long process.
According to A Social History of English, by Dick Leith,
West Saxon had seven recorded strong verb patterns. An example,
fleogan (fly), had five distinct vowel changes in its various tense-forms. As well as a past in fleag, and a past participle
flogen, there were vowel changed within each tense: in the present, the form was fliehþ after he, she, or it, and in the
past, flugon occurred after plural pronouns. Today, we find that the number of vowel changes has been reduced to three, so we get fly,
flew, flown. But in 'non-standard' speech, we often find a reduction
to two forms, so we hear I flown it, I done it, etc. Here the past
participle form is used for marking past tense.
It is customary, among historians of English when describing the
evolution of verb morphology, to attribute such changes to the
principle of analogy. [...] We find in recent dialect speech that
variation in verb forms is apparently endless, as different strong
verb patterns compete with the dominant weak ones. Finally, it is the
presence of that two-part weak pattern, present versus past, that may
account for the reduction to two forms in the strong verbs that
remain.
It is not only in broad dialect speech that the tendency to reduce
strong verb forms to two has occured. In my own speech, I have noted
hesitations about the past tense of drink; is it he drank, or he
drunk? The likelihood is that I will simplify the paradigm by using
the past participle form drunk for the simple past drank.
Sometimes, however, the process involves the reverse selection: in
Jane Austen's narrative, we sometimes find the past tense form used
for the past participle, as in the tables were broke up, and much
was ate. Thus, the process of simplification used to be as true of
so-called educated speech as it is today of dialect. What has happened
is that the tendency to reduce the forms of the verb to two has been
stigmatized. [...] It was the eighteenth-century codifiers [...] who
legitimized such sociolinguistic stratification by insisting that a
tripartite pattern in the strong verb was proper and correct from the
linguistic point of view. English, like Latin, they suggested, should
distinguish between past tense and past participle. The richer the
morphology the better; and one grammarian, Lowth, thought it essential
to restore inflections, and vowel-alternations, wherever it was
possible.
Another relevant paper I found is "The varieties of English spoken in the Southeast of England: morphology and syntax" by Lieselotte Anderwald.
As in many other dialect areas, many speakers in the Southeast have
verb paradigms different from the standard. [...] While each verb
undoubtedly has its own history, and many non-standard forms may be
carry-overs from historical forms that did not make it into the
standard, today non-standard grammar is often interpreted as
simplifying the StE system. Thus, three-part paradigms are reduced to
just two items – although it is not predictable whether the past tense
form or the past participle is extended to the other function – and we
also often find that two-part paradigms are reduced to just one form,
as in the cases of come or run.
