I wouldn't go quite that far. And much as English likes to blame its kookier aspects on other languages, English orthography being a mess has very little to do with loanwords--German has plenty of loanwords from French and usually retains the French spelling and at least an approximation of French pronunciation, yet its orthography is far more consistent--but instead is overwhelmingly due to historical sound shifts within English itself, and is particularly due to the fact that the English orthography we know and hate started to get, if not exactly standardized in the contemporary sense, at least laid down in a broad rule-of-thumb sense right in the middle of the Great Vowel Shift, but not before the shift was complete.J. J. W. Mezun wrote: ↑ raocow made a comment on yesterday’s video ’bout the “Enguard Kongtroversy” that he wanted to adapt it to sound mo’ like English, like how it seems French speakers do when they take foreign words ( & I know that Spanish does with foreign words ). This is interesting, as this concept doesn’t actually exist in English: English is just a mishmash o’ pronunciations from different languages with no consistent rules.
Speaking of language history, as a general rule, the older a loanword is, the more heavily it tends to be adapted to the loaning language, either in terms of its spelling being changed to fit the orthography of the loaning language (if it's a word initially more written than spoken), its spelling being changed to fit the pronunciation (if it's spoken more than written), or a bit of both. And indeed, for the most part, the French loanwords which have been most thoroughly anglicized in pronunciation are usually the ones that have been around the longest, whereas more recent loans, like "en guarde", tend to have a pronunciation which is closer to the original (if still frequently an approximation; "en garde" in English certainly hasn't changed to /ɛn gwɑ:(ɹ)d/, but it's not the original /ɑ̃ ɡaʁd/, either, English having neither nasal vowels nor /ʁ/, so speakers tend to settle on /ɑn ˈɡɑ:(ɹ)d/ as a compromise). Such is the case with other loans, like peetza or hal-uh-peenyo. And no one would ever think to rhyme "Pizza Hut" with "fizzer butt".
Another important thing to take in to account is that loanwords are affected by sound shifts, too, both in the loaning language, and the language of origin, which means the pronunciation in both the source and loaning language will inevitably start to drift over time. So when English speakers pronounce "judge" with an affricate /dʒ/ sound and not a pure fricative /ʒ/ sound like a good Frenchmen, it's not because they're slovenly degenerates, it's because that's how they've been pronouncing it since 1066. Indeed, we should should expect nothing other than /dʒ/, a that's the sound that French "juge" (or rather "iuge", as it would have initially been spelled, a distinct "j" character not really emerging until 1500 or so) was pronounced with in Old Norman French (reduction to /ʒ/ being a later development). And when that word was loaned in to English, it was the Old Norman French pronunciation--which was quite different from Modern Standard French--that the word was adopted with, and that's the pronunciation it kept, subsequent English sound shifts excepted.
Another thing to take in to account is that loanwords themselves can influence "normal" spelling in the language adopting them. Let's look again at "judge"...Funny word, that, spelling /dʒ/ with "j" and the start of the words, then with "dg" and a silent -e at the end. A lot of English words do that, come to think of it. I wonder why that is? It's doubly odd, considering the letter "J" is all other Germanic languages represents a "Y"-sound...the Y-sound is even written as /j/ in IPA*. Why did English start using "J" to represent /dʒ/, but only at the start of words?
Well, Old English, it turns out, did have /dʒ/, but only in the middle or at the end of words ( it comes from Proto-Germanic /ɣj/, which also never occurred word-initially). In Old English, this sound was written "ċġ" (usually without the diacritics), which becomes "dg" in modern spelling; compare Old English "eċġ" and modern English "edge", both pronounced the same and meaning the same thing (albeit usually only a sharp edge in OE; compare modern Danish "æg"). Old French, on the other hand, had no such compunctions about putting /dʒ/ at the start of words. Its own /dʒ/ came from Latin /j/ (again, a Y-sound), which occurs word-initially all the time, like in IVLIVS CAESAR. "ċġ" was not a combination English-speakers were used to seeing word-initially, however, and thus something like "ċġuċġ" looked inelegant. Since you only found this sound at the start of French words, though, why not use the French spelling? And that's what they did.
tldr: You anglicize old loanwords (like "judge" or "render"), but usually not newer ones (like "pizza" and "en guarde"), and most dumb things about English are based on domestic problems, so don't blame other languages for your homegrown sound shifts setting cock-a-hoop in your orthography.
* But why does English use the letter "Y" and not "J" to represent the phoneme /j/, then? Well, simply put, English *never* used the letter "J" (or "i"; remember, they were not consistently distinguished in writing at first) for that purpose. Of course Old English, like all Germanic languages, had lots of words that started with the /j/ sound--in fact it had more, since word-initial /g/, when immediately followed by /i/ or /e/, palatalized to /j/, which is why you have "yesterday in English but "Gestern" in German. So what did English start doing? It started writing them all with the letter "ġ", even when there was never historically a /g/ sound there to begin with, even when the next sound was not /i/ or /e/ (in which case they wrote a silent dummy "e" after the "g"). However, following the loaning of a great number of words with word-initially /ge/ and /gi/ from Old Norse, whether this represented /j/ or /g/ became increasingly ambiguous. Enter French.
How did French handle word-initial /j/ which hadn't been transformed to /dʒ/ (usually on account of being a later development)? It used "Y", which is to say Greek Upsilon, pronounced like German "ü" or French "u" in Ancient Greek (and transcribed as /y/ in IPA), but usually rendered as /i/ by those vulgar Latins. French already had "i" to represent /i/ (and would ultimately just use "u" to represent /y/ after /u/ shifted to /y/), of course, what was it to do with this spare upsilon? Just use it to represent the consonant equivalent of /i/, that is to say /j/.
Old English already used the letter "y", it should be stated, again for /y/, this ü-sound. However, in the Middle English period, this unrounded to /i/, so the letter "y" again became redundant. And thus the French use of "y" was adopted to fill the gap for word-initial /j/, regardless of whether it came from French, Proto-Germanic /j/, or palatalized Proto-Germanic /g/.