Question: Is this normal or should I go elsewhere?
Warning: Spoiler! (Click to show)
I've never had clothes altered before, but from reading online I didn't think any of these requests would pose a problem. But I was essentially told that none of my shirts could be altered because it will affect the shape of the shirt (I kind of thought that was the point of alteration, but didn't want to say anything). Specifically, the sleeves couldn't be brought in without making the arm hole smaller and higher, therefore making it impossible to move my arms.
Is this true, or should I take them somewhere else? (If so, where would you recommend?) Is it possible that the specific shirts I brought in wouldn't take well to alteration?
I also had a pair of pants that she said she couldn't make less baggy without closing half of the pocket, which confused me but by that point I was ready to leave.
As journey man has pointed out this advice is possibly correct and but it also is like many questions asked here, lacking context and an objective view of the interaction. That is not complete. However this is the internet and lack of knowledge never stops any opinions.
Basically anything can be altered in almost anyway - it may cost a small fortune or may throw out elements of the piece of clothing but it can be done.( I think theres a post back a few pages about altering an expensive dinner suit - also see the concept of "sunk costs" ) What your alterationist (its not clear if its a seamstress or tailor or alterations person - all are a bit different) has possibly done is to tell you in their own way that its not a positive cost benefit exercise given the "normal" price most people are willing to pay.
Slimming or taking in, a shirt below the armholes one of the easiest things to do . Hard to muck up even, unless you cut of excess before trying on and go too slim or do some silly things up near the armhole. Slimming/ taking in sleeves is a bit more technical. Running the machine down the seam and taking in the sleeve can be done in a quick and dirty way by veering (not technical speak) in to the armhole opening, so you might end up with a large armhole opening but slim sleeve and slim body - looking a bit odd. (OTOH if you keep your jacket on at all times no one will see it - but then they wont see your unaltered shirt either!)
In theory if you are slimming both the body and sleeve then you can make a smaller armhole at the same time ( I'm waving my hands around to show how and why) but then you are in the realm of expensive work and it would possibly be cheaper to buy a new shirt that fits.
Without being rude it might to be a good time to ask why you want THIS shirt slimmed so much and why not buy one that fits?
Trousers - depends how much taking in they need to make "less baggy" and where. Theres again a limit with trousers how much they can be altered around the general hips and thighs area without effecting pockets and other complicated things. Down below the hips,waist, thighs almost anything, cuffs, slimming leg etc, is a much simpler job.
Again it is worth asking are the pants special enough to risk ruining the look by seeking to make them too much what they are not and spending half the price of a new pair that fit?