There are guilds that suit for everyone. In retail there are guilds who require 2-5 alts. Guilds who doesn't require alts but requires you to farm m+ between raid days to get geared. There are guilds who require none of those above and will clear heroic in their own pace.
Same applies to Classic and TBC. You don't have to clear T4 week 1 just like you don't have to clear Heroic on retail week 1 (only 0.8% of raiding guilds cleared HC Denathrius week 1). Just find a guild that suits you.