With the reset of boosts you still are battling opponents within your old trophy range. You were artificially high in trophies due to boosts and the MM algorithm, this is the adjustment period.
You are currently at 5000 Trophies with a crew of average level 22. You likely boosted some that gave a huge stat increase due to boosts and gave a much lower “strength” rating due to rarity. Example: Boosting Epic, Rare and Legendary and they have now lost that MM and strength advantage. If you check other Alliances for teams in that range, they are about what you are battling, mid level 20’s Unique. You are likely being match on trophy count alone, as there are no teams within your “strength” MM zone now.
I am in the opposite aspect of the reset. I was artificially low in trophies because I did not boost, and now I am rising in trophies. With boosts, I was battling and losing to boosted level 17 to 20 Rare, Epic and Legendary. With the reset I am now automatically being matched with opponents in their new MM “strength” zone. My “strength” rating did not change, theirs did due to losing boosts. They were still all lower level but much higher in trophies. My opponents were being selected from the high end of my trophy count for MM. When I check my recent opponents, they are all much higher in trophies than I am. They will fall in trophies to find their new trophy range, as you will.
As I rose in Trophies, I started getting matched against opponents with similar creature levels. As you lose trophies you will start being matched against creatures more in line with your team level. You need to battle until you find your new trophy range in the new system.
I am curious what the visible trophy count of your opponents is.