Will Catholics ever return to mass?

It may be that Catholics have not been to a mass since the Novus Ordo, the new sacrament of ordination, and the new formula for consecrating bishops. That's over 50+ years too.

Marriage is essential for some. St. Paul teaches better to marry then to burn. Some will burn without marriage because of concupiscence.

I well know St Paul's words from Scripture, but again, what of those who want to marry but can't?  Paraplegics confined to bed or wheelchair who, even if they could perform the natural act, can't find anyone?  Women who are irredeemably ugly, fat, misshapen, deformed, have toxic personalities (their names are legion) or what have you?  Men with the same disadvantages?  Men who can't make enough money even to begin to support a wife and family?

I would hope that Our Lord would hear their cries, and alleviate their concupiscence in some way that doesn't involve sin, whatever that might be.

I'm reminded of what a priest once told me, "you don't mind bearing your crosses, as long as you get to pick them".

The question is:

Are most of these people Catholic in the first place?

Mass attendance is far from an indicator of orthodoxy.

https://www.pewresearch.org/fact-tank/2020/10/20/8-key-findings-about-catholics-and-abortion/

Of the few churches still open in my area, they are all trad, offering only the TLM.  The visitors from the N.O. are beginning to realize what they've been missing.  I think if/when there is a general re-opening, their new perspective will result in far reduced attendance at the N.O. (at some parishes) but increased at the TLM parishes and/or a demand for the traditional Mass at the old location.  One trad location I know of has seen a 50% increase in parish registration, strictly from those visiting from the N.O.

There is really no good reason to delay a proposed marriage where the prospective spouses would “burn”. Marriage should not be delayed indefinitely by an engaged couple. I can’t imagine however, having to get married for insurance or taxation etc. purposes.

If they were otherwise ready to get married, and the only obstacle were the unavailability of a priest, okay, I'll buy that.  I still think this is a bit of "catering" to people, and letting raw concupiscence rule the day, but neither would I be prepared to tell the entire population of a country (in a hypothetical situation) "no priests available in your country for Reason X for a year, well, that's just tough, consider this your cross to bear, no marriages for a year, God never gives us more than we can handle".  Two months without a priest, then passe-partout to marry privately before witnesses with sacred vows (I'd recommend witnesses and notarized statements, but that's just the wannabe lawyer in me, I guess), I can buy that, it's within the Church's authority of binding and loosing, end of story.  One can always make the case that just-married couples are so, shall we say, enthusiastic for one another --- this is all so "brand new" for them (or it should be, anyway, if they've been chaste during the engagement) that they will make very frequent use of their marital rights, and conceive a child in short order.  One hopes so, anyway.  As I always tell people, if you're not ready to have a child nine months after the wedding night (or at least to accept the possibility of it), then you're not ready to get married yet. In that case, then, yes, you just have to wait, concupiscence or no concupiscence.  Again, we are not cats in estrus, we are not rare-earth magnets that are irresistibly attracted to one another.

As for your second objection, quite the contrary, there are any number of good reasons, to need to be legally married.  The end of a tax year could be approaching, and you'd wish to be counted as married within that year, to obtain tax advantages.  There could be a situation of "getting one's spouse on one's insurance", military service or deployments where you wish your spouse to have commissary privileges and other military benefits, establishing joint tenancy for a real estate purchase, access to the spouse's pension, and so on.  Again, any number of good reasons. Though concupiscence isn't involved in any of these, they are, very possibly, more important "in the here and now" than the spiritual and moral reasons.  The law and the courts couldn't care less whether you're having sex with one another, but they do care whether you have a right to insurance, pensions, tax breaks, and the like.

Will Catholics Ever Return to Mass?

Not if they go to the Novus Ordo.