Then you deal with what you mentioned here not the absurd argument that the Bible writers didn't have lexicons. In fact you have given us a good reason to use lexicons.
I am fairly certain that many of the errors of people like Augustine, Gregory of Nyssa etc., if they exist, have been dealt with. And if they haven't that is why lexicons are a good idea. And just FYI there are about 800 words in good ol' king jimmy that have changed significantly or dropped out of use altogether.
My first Greek professor was Dr. Roger Omanson, now deceased, who was on the original NIV translation committee. He told us the struggles the committee had convincing the old school members to give up their often incorrect assumptions/presuppositions.
Here is a definition I looked up this afternoon. You may note the blue highlights. Those are the historical, lexical etc. sources the scholars consulted in determining the correct meaning. Honest scholars don't make up definitions which fit their assumptions/presuppositions.
μονογενής, ές (μόνος, γένος; Hes.; LXX; PsSol 18, 4; TestSol 20:2; TestBenj 9:2; ParJer 7:26; ApcEsdr 6:16; ApcSed 9:2; Joseph., Just.; loanw. in rabb.) acc. μονογενῆ (-ῆν J 3:16 v.l.; Hb 11:17 D; also ApcEsdr 6:16)
① pert. to being the only one of its kind within a specific relationship, one and only, only (so mostly, incl. Judg 11:34; Tob 3:15; 8:17) of children: of Isaac, Abraham’s only son (Jos., Ant. 1, 222) Hb 11:17. Of an only son (PsSol 18:4; TestSol 20:2; ParJer 7:26; Plut., Lycurgus 59 [31, 8]; Jos., Ant. 20, 20) Lk 7:12; 9:38. Of a daughter (Diod S 4, 73, 2) of Jairus 8:42. (On the motif of a child’s death before that of a parent s. EpigrAnat 13, ’89, 128f, no. 2; 18, ’91, 94 no. 4 [244/45 A.D.]; GVI nos. 1663–69.)
② pert. to being the only one of its kind or class, unique (in kind) of someth. that is the only example of its category (Cornutus 27 p, 49, 13 εἷς κ. μονογενὴς ὁ κόσμος ἐστί. μονογενῆ κ. μόνα ἐστίν=‘unique and alone’; Pla., Timaeus 92c; Theosophien 181, §56, 27). Of a mysterious bird, the Phoenix 1 Cl 25:2.—In the Johannine lit. (s. also ApcEsdr and ApcSed: ὁ μονογενής υἱός; Hippol., Ref. 8, 10, 3; Did., Gen. 89, 18; ὑμνοῦμέν γε θεὸν καὶ τὸν μ. αὐτοῦ Orig., C. Cels. 8, 67, 14; cp. ἡ δύναμις ἐκείνη ἡ μ. Hippol., Ref. 10, 16, 6) μονογενὴς υἱός is used only of Jesus. The renderings only, unique may be quite adequate for all its occurrences here (so M-M., NRSV et al.; DMoody, JBL 72, ’53, 213–19; FGrant, ATR 36, ’54, 284–87; GPendrick, NTS 41, ’95, 587–600). τὸν υἱὸν τὸν μ. ἔδωκεν J 3:16 (Philo Bybl. [100 A.D.]: 790 Fgm. 2 ch. 10, 33 Jac. [in Eus., PE 1, 10, 33]: Cronus offers up his μονογενὴς υἱός). ὁ μ. υἱὸς τοῦ θεοῦ vs. 18; τὸν υἱὸν τὸν μ. ἀπέσταλκεν ὁ θεός 1J 4:9; cp. Dg 10:2. On the expr. δόξαν ὡς μονογενοῦς παρὰ πατρός J 1:14 s. Hdb. ad loc. and PWinter, Zeitschrift für Rel. u. Geistesgeschichte 5, ’53, 335–65 (Engl.). See also Hdb. on vs. 18 where, beside the rdg. μονογενὴς θεός (considered by many the orig.) an only-begotten one, God (acc. to his real being; i.e. uniquely divine as God’s son and transcending all others alleged to be gods) or a uniquely begotten deity (for the perspective s. J 10:33–36), another rdg. ὁ μονογενὴς υἱός is found. MPol 20:2 in the doxology διὰ παιδὸς αὐτοῦ τοῦ μονογενοῦς Ἰησοῦ Χριστοῦ. Some (e.g. WBauer, Hdb.; JBulman, Calvin Theological Journal 16, ’81, 56–79; JDahms, NTS 29, ’83, 222–32) prefer to regard μ. as somewhat heightened in mng. in J and 1J to only-begotten or begotten of the Only One, in view of the emphasis on γεννᾶσθαι ἐκ θεοῦ (J 1:13 al.); in this case it would be analogous to πρωτότοκος (Ro 8:29; Col 1:15 al.).—On the mng. of μονογενής in history of religion s. the material in Hdb.3 25f on J 1:14 (also Plut., Mor. 423a Πλάτων … αὐτῷ δή φησι δοκεῖν ἕνα τοῦτον [sc. τὸν κόσμον] εἶναι μονογενῆ τῷ θεῷ καὶ ἀγαπητόν; Wsd 7:22 of σοφία: ἔστι ἐν αὐτῇ πνεῦμα νοερὸν ἅγιον μονογενές.—Vett. Val. 11, 32) as well as the lit. given there, also HLeisegang, Der Bruder des Erlösers: Αγγελος I 1925, 24–33; RBultmann J (comm., KEK) ’50, 47 n. 2; 55f.—DELG s.v. μένω. M-M. EDNT. TW. Sv.
William Arndt et al., A Greek-English Lexicon of the New Testament and Other Early Christian Literature (Chicago: University of Chicago Press, 2000), 658.