RAISE THE MOD CAP

While it's true that you have 6 Primaries on Triangles for those 8 Sets, you DON'T need every primary for every set.
As noted above there are many mismatches that make no sense.

For Example.

Crit Damage Triangle = ONLY 1 ACCEPTABLE PRIMARY = CRIT DAMAGE.
 (Okay, technically GAS has an option for CD/Protection combo but he's the only character I can think of that would want anything but CD on a CD-Triangle)

Offense Triangles are ONLY going to want Offense or CD.

Crit Chance Triangles are ONLY going to want Offense, CC, or CD.

Anything else is a mismatch & makes little sense.
Defense Triangles are almost always going to want Defense or Protection...... w/ maybe a few Def-Health or "Other" for some 1 off like GAS above.

Sure, Health you can run the full selection of options for the most part.  Maybe Tenacity & Potency too.  But everything else is going to be limited.

Arrows, sure Speed is KING.
But you're not likely to want a Defense Arrow w/ Offense primary.

I mean, I have a CritChance Cross w/ Defense Primary that is mostly useless but it also has like 19 speed so I find a home for it anyway.
But I'm certainly not going to keep any of those "mismatch" mods around w/ only 3 speed on them.

At this point in the game the worst mods I have are a few Potency+Potency Crosses w/ 5 Speed on them because I use them often & can't seem to get enough high speed ones.
After those few my "Minimum" for entire roster is like 7-8 & some Set/Type combos are 10+ for the worst characters.

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Look at it like this  (Puts on math/stats hat)

6 Mod Slots * 8 Families = 48 Mods * 10 Spare/Unequipped per Set/Family = 480 Unequipped mods.
Leaving you w/ 20 spare slots.   Enough for an event or 3 but you'll fill up every week or 2 for sure.  And only enough room for a couple loadout swaps before your full.

Also 3 Sets are "4-Mods" and Health is just super common, so I count it as a "4-Set".
The other 4 Sets are "2-Mods"

So, since you need more of the 4-Sets & will flat out have more Health from commonality.
You can also get by w/ a bare # of Square/Diamond since the Primary on those is fixed.
Circles only have 2 options, while Arrows have 7 but only 1 is a major contender w/ the other 6 being 1 offs.  So you'll need a few more but a ton.
Only Triangles & Crosses are actually in a place where you'll want a decent # of options.

SO, take that 10 above & to make some room you drop them down to something like this........

2 Mods = CC, Def, Pot, Ten
Square/Diamond = 4
Circle/Arrow = 5
Triangle/Cross = 6

4 Mods = CD, Off, Spd, & "Health" for commonness
Square/Diamond = 8
Circle/Arrow = 10
Triangle/Cross = 12

4 Families * (4+4+5+5+6+6) = 120
4 Families * (8+8+10+10+12+12) = 240
Total = 360 Unequipped Mods.

That is room for 140 "new" mods to show up in a week or 2 (or month or 2) and plenty of room for Mod Swapping.
I do some basic Level/Slice/Delete every week.
Every Month or 2 when that 360 Unequipped is now up in the 470 range I go in on a weekend & compare all those "new" mods to my existing & see what.
Maybe a new mod rolled a 7 but my minimum existing is a 9.  So the new one can be deleted same as if it rolled 0 or 3 speed.
Maybe a new mod rolled a 15 and can replace an existing minimum mod in the 7-10 range.

Point is, if your sitting on 20+ Health Squares UNEQUIPPED then you have entirely too many & you can afford to start deleting the low speed ones.