This is a serious drawback to the traditional math notation: if you didn't come up along one specific educational pathway, it seems to be effectively impossible to work your way in and figure out what any of it means. You can't pronounce any of it, you can't look it up; even if you can work out the names of the symbols, they often mean different things in different contexts. It is a mess.
For many years now, the way I have ingested CS papers is to read the introduction closely, getting my head around the concept, then bail out once the inscrutable symbols show up and go find an actual implementation in some real, documented, parseable programming language - any one will do - from which I can readily infer what the rest of the paper was supposed to mean.
Even in our own field, Computer Science, there are too many confusing cases: Knuth uses |S| to mean the cardinality of set S, |f| to be the number of solutions when f is a boolean, |x| to be the absolute value of x, |z| to be the absolute value of a complex number, and |a| to be the length of a. All within the same book, TAOCP vol 4A Part 1.
What "the size of" means is different applied to each type of object, and may have to be defined to explain some of them (esp. |f|), but it's common in math that general concepts apply differently to different things, while having some properties in common.
I think the notation is helpful rather than confusing because "the size of" carries with it some intuitive connotations which are common to each of those examples.
tldr; it’s tedious reading those proofs. And it’s laborious to write them. Such labour limits the thoughts one can have. Once algebra has solidified there was an explosion in the pace and depth of mathematics.
The symbols are there for a good reason.
In fact, it’s pretty common for math students to want to use only symbols at some point. What they write becomes unintelligible to everyone else (and maybe even themselves) and at some point they (usually) wise up.
It is kind of like everyone in the 60s decided that APL was the one true computer language and all interest in other languages died off entirely and when anybody complains about the syntax they are told that they just need to go to school for 4 years and they'll appreciate the beauty.