Apprasing pidgeys rattatas...

I've had the opposite problem, until a few months ago I was clueless I had a 98% Arcanine, 98% Exeggutor, and 98% Charizard. I at least now have the A and E to level 30...Charizard is still at level 20. I caught a 100% Ekans that was level 28 I immediately noticed, gonna need another (longer) stardust event to get that to 30 though

I'm doing that too, because until now I still haven't caught any 100% mons.

I compulsively appraise everything i catch

I don't appraise them when I catch but i do check the top 5 or 6 cp mons once they have been evolved.

I have a L26/91% Pidgeot, a L26/84% Pidgeot and a L30/95% Raticate that occasionally get put in gyms, just because I get bored of seeing all the usual stuff. None have been powered up.

I generally appraise anything that is high CP, not bothering with those at the lower end of the scale. Pokemon that are rarer, or very valuable in the meta, I will usually appraise all of them.

Pidgey and Rattata, I don't bother at all with. At the rate I get them I figure that, on the remote possibility they ever become valuable in battle, I can just find a strong one easily enough.

I check once in a while , all above 82% get the favorite star rest to prof. Willow. When bag is full again i check all iv's of favorite , all under 91% goes again to prof. Some like natu pidgey rattata and so i tranfer all under 96%.

If I don’t have the time, I’ll just transfer all the useless mons without checking. The only downside is that you may transfer a 100, but as the earlier poster said, I too have 100 Pidgey (25 CP) that just takes up space.

I wish there was a feature where mons would be highlighted in different color based on appraisal level.

I appraise everything, keep the highest IV one of each (unless it's a dimorphic species or a shiny, in which case shiny and other morph are kept in place until I get better ones for those spots too). I aim to get as many 100%s as I can.
Current 100% IV collection:

The only thing I don't bother appraising anymore is Ledyba/Ledian, I've managed 2 perfect ledybas and 1 perfect ledian (not a brag, cuz those aren't worth bragging about). I want to keep a full dex colection, and even if the mon is not worth using, I like to keep the best/highest IV version of everything I find, regardless of level/CP, so I would keep that Pidgeot if I were you, 3.72.

Edit: A silly/memeish part of me also REALLY wants a perfect IV Rattata, I would nickname it "Joey's".