Realistically speaking... solo 5 star raids are a coinflip even with a lvl 100 mon. Low powered ones are doable, I've beat "solo" stuff like eevee, zoroark, couple more, but even chonky pokemon like toxapex can be a challenge cause NPCs don't teralyze so will not really be able to break the barrier
Do them with people. Sometimes you get the player with lvl 60 just caught throwing, but from my experience *most* of the time you get people who either are aiming for the oneshot, or at very least know what they're doing.
Don't even bother trying to solo lvl 6s. Not happening.
Interestingly, this would match with both my playthroughs (the one on the ROM and the one on the actual game).
In the one with the ROM, where I did a lot of picnicing for testing breeding, we eventually toward the end had our pokemon throw affection things.
However in my current one I have yet to witness a single affection trigger, even from the starter I have since basically the start of the game. I have only used picnic like twice to make some eggs for friends / pass egg moves, and all times I used sandwitches from shops and not handmade.