You're not going to get support for this from 6+ years players that are competitive primarily because they know that good-mod acquisition and recycling doesn't really need to fill an inventory.
There are highly respected SWGOH-Youtubers/players that have sub-channels dedicated in Discord for how to manage mods the most intelligently based off of likelihood of rolls statistics. When you farm and upgrade based off of these principles, you're simply not going to fill an inventory.
Would I like the mod inventory to be bigger? Yes. Is it necessary? Really far from it. The seasoned players I am referring to won't really view what I've told you as an opinion. Youtube search "Fatal Playbook SWGOH", find his most recent video and click on "more" to get his Discord join link. Join and go to his "Mod" sub-channel. His infographics on mod-acquisition are really good.
If you'd like to chat more about it in Discord with me I can walk you through how to be more sensibly selective with daily 3x50 refreshes on mod-battles each day. My top 110 modscore is 14.25 at 10.7 million GP. Lots of players would like my mod score and depth. I don't have a perfect system but it's really good for a guy that quit playing for 4 years. I can talk you through all of it.